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Merge branch 'writeback-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux

Browse source 
* 'writeback-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux:
  writeback: Add a 'reason' to wb_writeback_work
  writeback: send work item to queue_io, move_expired_inodes
  writeback: trace event balance_dirty_pages
  writeback: trace event bdi_dirty_ratelimit
  writeback: fix ppc compile warnings on do_div(long long, unsigned long)
  writeback: per-bdi background threshold
  writeback: dirty position control - bdi reserve area
  writeback: control dirty pause time
  writeback: limit max dirty pause time
  writeback: IO-less balance_dirty_pages()
  writeback: per task dirty rate limit
  writeback: stabilize bdi->dirty_ratelimit
  writeback: dirty rate control
  writeback: add bg_threshold parameter to __bdi_update_bandwidth()
  writeback: dirty position control
  writeback: account per-bdi accumulated dirtied pages
This commit is contained in:
Linus Torvalds 2011-11-06 19:02:23 -08:00
commit 208bca0860
15 changed files with 807 additions and 226 deletions
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3
fs/btrfs/extent-tree.c
View file

@ -3340,7 +3340,8 @@ static int shrink_delalloc(struct btrfs_trans_handle *trans,
smp_mb();
nr_pages = min_t(unsigned long, nr_pages,
root->fs_info->delalloc_bytes >> PAGE_CACHE_SHIFT);
writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages);
writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages,
WB_REASON_FS_FREE_SPACE);
spin_lock(&space_info->lock);
if (reserved > space_info->bytes_reserved)

2
fs/buffer.c
View file

@ -288,7 +288,7 @@ static void free_more_memory(void)
struct zone *zone;
int nid;
wakeup_flusher_threads(1024);
wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
yield();
for_each_online_node(nid) {

2
fs/ext4/inode.c
View file

@ -2372,7 +2372,7 @@ static int ext4_nonda_switch(struct super_block *sb)
* start pushing delalloc when 1/2 of free blocks are dirty.
*/
if (free_blocks < 2 * dirty_blocks)
writeback_inodes_sb_if_idle(sb);
writeback_inodes_sb_if_idle(sb, WB_REASON_FS_FREE_SPACE);
return 0;
}

84
fs/fs-writeback.c
View file

@ -41,11 +41,23 @@ struct wb_writeback_work {
unsigned int for_kupdate:1;
unsigned int range_cyclic:1;
unsigned int for_background:1;
enum wb_reason reason; /* why was writeback initiated? */
struct list_head list; /* pending work list */
struct completion *done; /* set if the caller waits */
};
const char *wb_reason_name[] = {
[WB_REASON_BACKGROUND] = "background",
[WB_REASON_TRY_TO_FREE_PAGES] = "try_to_free_pages",
[WB_REASON_SYNC] = "sync",
[WB_REASON_PERIODIC] = "periodic",
[WB_REASON_LAPTOP_TIMER] = "laptop_timer",
[WB_REASON_FREE_MORE_MEM] = "free_more_memory",
[WB_REASON_FS_FREE_SPACE] = "fs_free_space",
[WB_REASON_FORKER_THREAD] = "forker_thread"
};
/*
* Include the creation of the trace points after defining the
* wb_writeback_work structure so that the definition remains local to this
@ -115,7 +127,7 @@ static void bdi_queue_work(struct backing_dev_info *bdi,
static void
__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
bool range_cyclic)
bool range_cyclic, enum wb_reason reason)
{
struct wb_writeback_work *work;
@ -135,6 +147,7 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
work->sync_mode = WB_SYNC_NONE;
work->nr_pages = nr_pages;
work->range_cyclic = range_cyclic;
work->reason = reason;
bdi_queue_work(bdi, work);
}
@ -150,9 +163,10 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
* completion. Caller need not hold sb s_umount semaphore.
*
*/
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
enum wb_reason reason)
{
__bdi_start_writeback(bdi, nr_pages, true);
__bdi_start_writeback(bdi, nr_pages, true, reason);
}
/**
@ -251,7 +265,7 @@ static bool inode_dirtied_after(struct inode *inode, unsigned long t)
*/
static int move_expired_inodes(struct list_head *delaying_queue,
struct list_head *dispatch_queue,
unsigned long *older_than_this)
struct wb_writeback_work *work)
{
LIST_HEAD(tmp);
struct list_head *pos, *node;
@ -262,8 +276,8 @@ static int move_expired_inodes(struct list_head *delaying_queue,
while (!list_empty(delaying_queue)) {
inode = wb_inode(delaying_queue->prev);
if (older_than_this &&
inode_dirtied_after(inode, *older_than_this))
if (work->older_than_this &&
inode_dirtied_after(inode, *work->older_than_this))
break;
if (sb && sb != inode->i_sb)
do_sb_sort = 1;
@ -302,13 +316,13 @@ static int move_expired_inodes(struct list_head *delaying_queue,
* |
* +--> dequeue for IO
*/
static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
static void queue_io(struct bdi_writeback *wb, struct wb_writeback_work *work)
{
int moved;
assert_spin_locked(&wb->list_lock);
list_splice_init(&wb->b_more_io, &wb->b_io);
moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
trace_writeback_queue_io(wb, older_than_this, moved);
moved = move_expired_inodes(&wb->b_dirty, &wb->b_io, work);
trace_writeback_queue_io(wb, work, moved);
}
static int write_inode(struct inode *inode, struct writeback_control *wbc)
@ -641,31 +655,40 @@ static long __writeback_inodes_wb(struct bdi_writeback *wb,
return wrote;
}
long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages)
long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
enum wb_reason reason)
{
struct wb_writeback_work work = {
.nr_pages = nr_pages,
.sync_mode = WB_SYNC_NONE,
.range_cyclic = 1,
.reason = reason,
};
spin_lock(&wb->list_lock);
if (list_empty(&wb->b_io))
queue_io(wb, NULL);
queue_io(wb, &work);
__writeback_inodes_wb(wb, &work);
spin_unlock(&wb->list_lock);
return nr_pages - work.nr_pages;
}
static inline bool over_bground_thresh(void)
static bool over_bground_thresh(struct backing_dev_info *bdi)
{
unsigned long background_thresh, dirty_thresh;
global_dirty_limits(&background_thresh, &dirty_thresh);
return (global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) > background_thresh);
if (global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) > background_thresh)
return true;
if (bdi_stat(bdi, BDI_RECLAIMABLE) >
bdi_dirty_limit(bdi, background_thresh))
return true;
return false;
}
/*
@ -675,7 +698,7 @@ static inline bool over_bground_thresh(void)
static void wb_update_bandwidth(struct bdi_writeback *wb,
unsigned long start_time)
{
__bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, start_time);
__bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
}
/*
@ -727,7 +750,7 @@ static long wb_writeback(struct bdi_writeback *wb,
* For background writeout, stop when we are below the
* background dirty threshold
*/
if (work->for_background && !over_bground_thresh())
if (work->for_background && !over_bground_thresh(wb->bdi))
break;
if (work->for_kupdate) {
@ -738,7 +761,7 @@ static long wb_writeback(struct bdi_writeback *wb,
trace_writeback_start(wb->bdi, work);
if (list_empty(&wb->b_io))
queue_io(wb, work->older_than_this);
queue_io(wb, work);
if (work->sb)
progress = writeback_sb_inodes(work->sb, wb, work);
else
@ -811,13 +834,14 @@ static unsigned long get_nr_dirty_pages(void)
static long wb_check_background_flush(struct bdi_writeback *wb)
{
if (over_bground_thresh()) {
if (over_bground_thresh(wb->bdi)) {
struct wb_writeback_work work = {
.nr_pages = LONG_MAX,
.sync_mode = WB_SYNC_NONE,
.for_background = 1,
.range_cyclic = 1,
.reason = WB_REASON_BACKGROUND,
};
return wb_writeback(wb, &work);
@ -851,6 +875,7 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
.sync_mode = WB_SYNC_NONE,
.for_kupdate = 1,
.range_cyclic = 1,
.reason = WB_REASON_PERIODIC,
};
return wb_writeback(wb, &work);
@ -969,7 +994,7 @@ int bdi_writeback_thread(void *data)
* Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
* the whole world.
*/
void wakeup_flusher_threads(long nr_pages)
void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
{
struct backing_dev_info *bdi;
@ -982,7 +1007,7 @@ void wakeup_flusher_threads(long nr_pages)
list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
if (!bdi_has_dirty_io(bdi))
continue;
__bdi_start_writeback(bdi, nr_pages, false);
__bdi_start_writeback(bdi, nr_pages, false, reason);
}
rcu_read_unlock();
}
@ -1203,7 +1228,9 @@ static void wait_sb_inodes(struct super_block *sb)
* on how many (if any) will be written, and this function does not wait
* for IO completion of submitted IO.
*/
void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
void writeback_inodes_sb_nr(struct super_block *sb,
unsigned long nr,
enum wb_reason reason)
{
DECLARE_COMPLETION_ONSTACK(done);
struct wb_writeback_work work = {
@ -1212,6 +1239,7 @@ void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr)
.tagged_writepages = 1,
.done = &done,
.nr_pages = nr,
.reason = reason,
};
WARN_ON(!rwsem_is_locked(&sb->s_umount));
@ -1228,9 +1256,9 @@ EXPORT_SYMBOL(writeback_inodes_sb_nr);
* on how many (if any) will be written, and this function does not wait
* for IO completion of submitted IO.
*/
void writeback_inodes_sb(struct super_block *sb)
void writeback_inodes_sb(struct super_block *sb, enum wb_reason reason)
{
return writeback_inodes_sb_nr(sb, get_nr_dirty_pages());
return writeback_inodes_sb_nr(sb, get_nr_dirty_pages(), reason);
}
EXPORT_SYMBOL(writeback_inodes_sb);
@ -1241,11 +1269,11 @@ EXPORT_SYMBOL(writeback_inodes_sb);
* Invoke writeback_inodes_sb if no writeback is currently underway.
* Returns 1 if writeback was started, 0 if not.
*/
int writeback_inodes_sb_if_idle(struct super_block *sb)
int writeback_inodes_sb_if_idle(struct super_block *sb, enum wb_reason reason)
{
if (!writeback_in_progress(sb->s_bdi)) {
down_read(&sb->s_umount);
writeback_inodes_sb(sb);
writeback_inodes_sb(sb, reason);
up_read(&sb->s_umount);
return 1;
} else
@ -1262,11 +1290,12 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
* Returns 1 if writeback was started, 0 if not.
*/
int writeback_inodes_sb_nr_if_idle(struct super_block *sb,
unsigned long nr)
unsigned long nr,
enum wb_reason reason)
{
if (!writeback_in_progress(sb->s_bdi)) {
down_read(&sb->s_umount);
writeback_inodes_sb_nr(sb, nr);
writeback_inodes_sb_nr(sb, nr, reason);
up_read(&sb->s_umount);
return 1;
} else
@ -1290,6 +1319,7 @@ void sync_inodes_sb(struct super_block *sb)
.nr_pages = LONG_MAX,
.range_cyclic = 0,
.done = &done,
.reason = WB_REASON_SYNC,
};
WARN_ON(!rwsem_is_locked(&sb->s_umount));

2
fs/quota/quota.c
View file

@ -286,7 +286,7 @@ static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id,
/* caller already holds s_umount */
if (sb->s_flags & MS_RDONLY)
return -EROFS;
writeback_inodes_sb(sb);
writeback_inodes_sb(sb, WB_REASON_SYNC);
return 0;
default:
return -EINVAL;

4
fs/sync.c
View file

@ -43,7 +43,7 @@ static int __sync_filesystem(struct super_block *sb, int wait)
if (wait)
sync_inodes_sb(sb);
else
writeback_inodes_sb(sb);
writeback_inodes_sb(sb, WB_REASON_SYNC);
if (sb->s_op->sync_fs)
sb->s_op->sync_fs(sb, wait);
@ -98,7 +98,7 @@ static void sync_filesystems(int wait)
*/
SYSCALL_DEFINE0(sync)
{
wakeup_flusher_threads(0);
wakeup_flusher_threads(0, WB_REASON_SYNC);
sync_filesystems(0);
sync_filesystems(1);
if (unlikely(laptop_mode))

2
fs/ubifs/budget.c
View file

@ -63,7 +63,7 @@
static void shrink_liability(struct ubifs_info *c, int nr_to_write)
{
down_read(&c->vfs_sb->s_umount);
writeback_inodes_sb(c->vfs_sb);
writeback_inodes_sb(c->vfs_sb, WB_REASON_FS_FREE_SPACE);
up_read(&c->vfs_sb->s_umount);
}

14
include/linux/backing-dev.h
View file

@ -40,6 +40,7 @@ typedef int (congested_fn)(void *, int);
enum bdi_stat_item {
BDI_RECLAIMABLE,
BDI_WRITEBACK,
BDI_DIRTIED,
BDI_WRITTEN,
NR_BDI_STAT_ITEMS
};
@ -74,10 +75,20 @@ struct backing_dev_info {
struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
unsigned long bw_time_stamp; /* last time write bw is updated */
unsigned long dirtied_stamp;
unsigned long written_stamp; /* pages written at bw_time_stamp */
unsigned long write_bandwidth; /* the estimated write bandwidth */
unsigned long avg_write_bandwidth; /* further smoothed write bw */
/*
* The base dirty throttle rate, re-calculated on every 200ms.
* All the bdi tasks' dirty rate will be curbed under it.
* @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
* in small steps and is much more smooth/stable than the latter.
*/
unsigned long dirty_ratelimit;
unsigned long balanced_dirty_ratelimit;
struct prop_local_percpu completions;
int dirty_exceeded;
@ -107,7 +118,8 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
void bdi_unregister(struct backing_dev_info *bdi);
int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages);
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
enum wb_reason reason);
void bdi_start_background_writeback(struct backing_dev_info *bdi);
int bdi_writeback_thread(void *data);
int bdi_has_dirty_io(struct backing_dev_info *bdi);

7
include/linux/sched.h
View file

@ -1522,6 +1522,13 @@ struct task_struct {
int make_it_fail;
#endif
struct prop_local_single dirties;
/*
* when (nr_dirtied >= nr_dirtied_pause), it's time to call
* balance_dirty_pages() for some dirty throttling pause
*/
int nr_dirtied;
int nr_dirtied_pause;
#ifdef CONFIG_LATENCYTOP
int latency_record_count;
struct latency_record latency_record[LT_SAVECOUNT];

33
include/linux/writeback.h
View file

@ -38,6 +38,23 @@ enum writeback_sync_modes {
WB_SYNC_ALL, /* Wait on every mapping */
};
/*
* why some writeback work was initiated
*/
enum wb_reason {
WB_REASON_BACKGROUND,
WB_REASON_TRY_TO_FREE_PAGES,
WB_REASON_SYNC,
WB_REASON_PERIODIC,
WB_REASON_LAPTOP_TIMER,
WB_REASON_FREE_MORE_MEM,
WB_REASON_FS_FREE_SPACE,
WB_REASON_FORKER_THREAD,
WB_REASON_MAX,
};
extern const char *wb_reason_name[];
/*
* A control structure which tells the writeback code what to do. These are
* always on the stack, and hence need no locking. They are always initialised
@ -69,14 +86,17 @@ struct writeback_control {
*/
struct bdi_writeback;
int inode_wait(void *);
void writeback_inodes_sb(struct super_block *);
void writeback_inodes_sb_nr(struct super_block *, unsigned long nr);
int writeback_inodes_sb_if_idle(struct super_block *);
int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr);
void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
enum wb_reason reason);
int writeback_inodes_sb_if_idle(struct super_block *, enum wb_reason reason);
int writeback_inodes_sb_nr_if_idle(struct super_block *, unsigned long nr,
enum wb_reason reason);
void sync_inodes_sb(struct super_block *);
long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages);
long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
enum wb_reason reason);
long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
void wakeup_flusher_threads(long nr_pages);
void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
/* writeback.h requires fs.h; it, too, is not included from here. */
static inline void wait_on_inode(struct inode *inode)
@ -143,6 +163,7 @@ unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
void __bdi_update_bandwidth(struct backing_dev_info *bdi,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
unsigned long bdi_thresh,
unsigned long bdi_dirty,

161
include/trace/events/writeback.h
View file

@ -34,6 +34,7 @@ DECLARE_EVENT_CLASS(writeback_work_class,
__field(int, for_kupdate)
__field(int, range_cyclic)
__field(int, for_background)
__field(int, reason)
),
TP_fast_assign(
strncpy(__entry->name, dev_name(bdi->dev), 32);
@ -43,16 +44,18 @@ DECLARE_EVENT_CLASS(writeback_work_class,
__entry->for_kupdate = work->for_kupdate;
__entry->range_cyclic = work->range_cyclic;
__entry->for_background = work->for_background;
__entry->reason = work->reason;
),
TP_printk("bdi %s: sb_dev %d:%d nr_pages=%ld sync_mode=%d "
"kupdate=%d range_cyclic=%d background=%d",
"kupdate=%d range_cyclic=%d background=%d reason=%s",
__entry->name,
MAJOR(__entry->sb_dev), MINOR(__entry->sb_dev),
__entry->nr_pages,
__entry->sync_mode,
__entry->for_kupdate,
__entry->range_cyclic,
__entry->for_background
__entry->for_background,
wb_reason_name[__entry->reason]
)
);
#define DEFINE_WRITEBACK_WORK_EVENT(name) \
@ -104,30 +107,6 @@ DEFINE_WRITEBACK_EVENT(writeback_bdi_register);
DEFINE_WRITEBACK_EVENT(writeback_bdi_unregister);
DEFINE_WRITEBACK_EVENT(writeback_thread_start);
DEFINE_WRITEBACK_EVENT(writeback_thread_stop);
DEFINE_WRITEBACK_EVENT(balance_dirty_start);
DEFINE_WRITEBACK_EVENT(balance_dirty_wait);
TRACE_EVENT(balance_dirty_written,
TP_PROTO(struct backing_dev_info *bdi, int written),
TP_ARGS(bdi, written),
TP_STRUCT__entry(
__array(char, name, 32)
__field(int, written)
),
TP_fast_assign(
strncpy(__entry->name, dev_name(bdi->dev), 32);
__entry->written = written;
),
TP_printk("bdi %s written %d",
__entry->name,
__entry->written
)
);
DECLARE_EVENT_CLASS(wbc_class,
TP_PROTO(struct writeback_control *wbc, struct backing_dev_info *bdi),
@ -181,27 +160,31 @@ DEFINE_WBC_EVENT(wbc_writepage);
TRACE_EVENT(writeback_queue_io,
TP_PROTO(struct bdi_writeback *wb,
unsigned long *older_than_this,
struct wb_writeback_work *work,
int moved),
TP_ARGS(wb, older_than_this, moved),
TP_ARGS(wb, work, moved),
TP_STRUCT__entry(
__array(char, name, 32)
__field(unsigned long, older)
__field(long, age)
__field(int, moved)
__field(int, reason)
),
TP_fast_assign(
unsigned long *older_than_this = work->older_than_this;
strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
__entry->older = older_than_this ? *older_than_this : 0;
__entry->age = older_than_this ?
(jiffies - *older_than_this) * 1000 / HZ : -1;
__entry->moved = moved;
__entry->reason = work->reason;
),
TP_printk("bdi %s: older=%lu age=%ld enqueue=%d",
TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s",
__entry->name,
__entry->older, /* older_than_this in jiffies */
__entry->age, /* older_than_this in relative milliseconds */
__entry->moved)
__entry->moved,
wb_reason_name[__entry->reason])
);
TRACE_EVENT(global_dirty_state,
@ -250,6 +233,124 @@ TRACE_EVENT(global_dirty_state,
)
);
#define KBps(x) ((x) << (PAGE_SHIFT - 10))
TRACE_EVENT(bdi_dirty_ratelimit,
TP_PROTO(struct backing_dev_info *bdi,
unsigned long dirty_rate,
unsigned long task_ratelimit),
TP_ARGS(bdi, dirty_rate, task_ratelimit),
TP_STRUCT__entry(
__array(char, bdi, 32)
__field(unsigned long, write_bw)
__field(unsigned long, avg_write_bw)
__field(unsigned long, dirty_rate)
__field(unsigned long, dirty_ratelimit)
__field(unsigned long, task_ratelimit)
__field(unsigned long, balanced_dirty_ratelimit)
),
TP_fast_assign(
strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
__entry->write_bw = KBps(bdi->write_bandwidth);
__entry->avg_write_bw = KBps(bdi->avg_write_bandwidth);
__entry->dirty_rate = KBps(dirty_rate);
__entry->dirty_ratelimit = KBps(bdi->dirty_ratelimit);
__entry->task_ratelimit = KBps(task_ratelimit);
__entry->balanced_dirty_ratelimit =
KBps(bdi->balanced_dirty_ratelimit);
),
TP_printk("bdi %s: "
"write_bw=%lu awrite_bw=%lu dirty_rate=%lu "
"dirty_ratelimit=%lu task_ratelimit=%lu "
"balanced_dirty_ratelimit=%lu",
__entry->bdi,
__entry->write_bw, /* write bandwidth */
__entry->avg_write_bw, /* avg write bandwidth */
__entry->dirty_rate, /* bdi dirty rate */
__entry->dirty_ratelimit, /* base ratelimit */
__entry->task_ratelimit, /* ratelimit with position control */
__entry->balanced_dirty_ratelimit /* the balanced ratelimit */
)
);
TRACE_EVENT(balance_dirty_pages,
TP_PROTO(struct backing_dev_info *bdi,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
unsigned long bdi_thresh,
unsigned long bdi_dirty,
unsigned long dirty_ratelimit,
unsigned long task_ratelimit,
unsigned long dirtied,
long pause,
unsigned long start_time),
TP_ARGS(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty,
dirty_ratelimit, task_ratelimit,
dirtied, pause, start_time),
TP_STRUCT__entry(
__array( char, bdi, 32)
__field(unsigned long, limit)
__field(unsigned long, setpoint)
__field(unsigned long, dirty)
__field(unsigned long, bdi_setpoint)
__field(unsigned long, bdi_dirty)
__field(unsigned long, dirty_ratelimit)
__field(unsigned long, task_ratelimit)
__field(unsigned int, dirtied)
__field(unsigned int, dirtied_pause)
__field(unsigned long, paused)
__field( long, pause)
),
TP_fast_assign(
unsigned long freerun = (thresh + bg_thresh) / 2;
strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
__entry->limit = global_dirty_limit;
__entry->setpoint = (global_dirty_limit + freerun) / 2;
__entry->dirty = dirty;
__entry->bdi_setpoint = __entry->setpoint *
bdi_thresh / (thresh + 1);
__entry->bdi_dirty = bdi_dirty;
__entry->dirty_ratelimit = KBps(dirty_ratelimit);
__entry->task_ratelimit = KBps(task_ratelimit);
__entry->dirtied = dirtied;
__entry->dirtied_pause = current->nr_dirtied_pause;
__entry->pause = pause * 1000 / HZ;
__entry->paused = (jiffies - start_time) * 1000 / HZ;
),
TP_printk("bdi %s: "
"limit=%lu setpoint=%lu dirty=%lu "
"bdi_setpoint=%lu bdi_dirty=%lu "
"dirty_ratelimit=%lu task_ratelimit=%lu "
"dirtied=%u dirtied_pause=%u "
"paused=%lu pause=%ld",
__entry->bdi,
__entry->limit,
__entry->setpoint,
__entry->dirty,
__entry->bdi_setpoint,
__entry->bdi_dirty,
__entry->dirty_ratelimit,
__entry->task_ratelimit,
__entry->dirtied,
__entry->dirtied_pause,
__entry->paused, /* ms */
__entry->pause /* ms */
)
);
DECLARE_EVENT_CLASS(writeback_congest_waited_template,
TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),

3
kernel/fork.c
View file

@ -1299,6 +1299,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->pdeath_signal = 0;
p->exit_state = 0;
p->nr_dirtied = 0;
p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
/*
* Ok, make it visible to the rest of the system.
* We dont wake it up yet.

7
mm/backing-dev.c
View file

@ -97,6 +97,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
"BdiDirtyThresh: %10lu kB\n"
"DirtyThresh: %10lu kB\n"
"BackgroundThresh: %10lu kB\n"
"BdiDirtied: %10lu kB\n"
"BdiWritten: %10lu kB\n"
"BdiWriteBandwidth: %10lu kBps\n"
"b_dirty: %10lu\n"
@ -109,6 +110,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
K(bdi_thresh),
K(dirty_thresh),
K(background_thresh),
(unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),
(unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
(unsigned long) K(bdi->write_bandwidth),
nr_dirty,
@ -473,7 +475,8 @@ static int bdi_forker_thread(void *ptr)
* the bdi from the thread. Hopefully 1024 is
* large enough for efficient IO.
*/
writeback_inodes_wb(&bdi->wb, 1024);
writeback_inodes_wb(&bdi->wb, 1024,
WB_REASON_FORKER_THREAD);
} else {
/*
* The spinlock makes sure we do not lose
@ -683,6 +686,8 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->bw_time_stamp = jiffies;
bdi->written_stamp = 0;
bdi->balanced_dirty_ratelimit = INIT_BW;
bdi->dirty_ratelimit = INIT_BW;
bdi->write_bandwidth = INIT_BW;
bdi->avg_write_bandwidth = INIT_BW;

706
mm/page-writeback.c
View file

@ -46,26 +46,14 @@
*/
#define BANDWIDTH_INTERVAL max(HZ/5, 1)
#define RATELIMIT_CALC_SHIFT 10
/*
* After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
* will look to see if it needs to force writeback or throttling.
*/
static long ratelimit_pages = 32;
/*
* When balance_dirty_pages decides that the caller needs to perform some
* non-background writeback, this is how many pages it will attempt to write.
* It should be somewhat larger than dirtied pages to ensure that reasonably
* large amounts of I/O are submitted.
*/
static inline long sync_writeback_pages(unsigned long dirtied)
{
if (dirtied < ratelimit_pages)
dirtied = ratelimit_pages;
return dirtied + dirtied / 2;
}
/* The following parameters are exported via /proc/sys/vm */
/*
@ -167,6 +155,8 @@ static void update_completion_period(void)
int shift = calc_period_shift();
prop_change_shift(&vm_completions, shift);
prop_change_shift(&vm_dirties, shift);
writeback_set_ratelimit();
}
int dirty_background_ratio_handler(struct ctl_table *table, int write,
@ -260,50 +250,6 @@ static void bdi_writeout_fraction(struct backing_dev_info *bdi,
numerator, denominator);
}
static inline void task_dirties_fraction(struct task_struct *tsk,
long *numerator, long *denominator)
{
prop_fraction_single(&vm_dirties, &tsk->dirties,
numerator, denominator);
}
/*
* task_dirty_limit - scale down dirty throttling threshold for one task
*
* task specific dirty limit:
*
* dirty -= (dirty/8) * p_{t}
*
* To protect light/slow dirtying tasks from heavier/fast ones, we start
* throttling individual tasks before reaching the bdi dirty limit.
* Relatively low thresholds will be allocated to heavy dirtiers. So when
* dirty pages grow large, heavy dirtiers will be throttled first, which will
* effectively curb the growth of dirty pages. Light dirtiers with high enough
* dirty threshold may never get throttled.
*/
#define TASK_LIMIT_FRACTION 8
static unsigned long task_dirty_limit(struct task_struct *tsk,
unsigned long bdi_dirty)
{
long numerator, denominator;
unsigned long dirty = bdi_dirty;
u64 inv = dirty / TASK_LIMIT_FRACTION;
task_dirties_fraction(tsk, &numerator, &denominator);
inv *= numerator;
do_div(inv, denominator);
dirty -= inv;
return max(dirty, bdi_dirty/2);
}
/* Minimum limit for any task */
static unsigned long task_min_dirty_limit(unsigned long bdi_dirty)
{
return bdi_dirty - bdi_dirty / TASK_LIMIT_FRACTION;
}
/*
* bdi_min_ratio keeps the sum of the minimum dirty shares of all
* registered backing devices, which, for obvious reasons, can not
@ -413,6 +359,12 @@ unsigned long determine_dirtyable_memory(void)
return x + 1; /* Ensure that we never return 0 */
}
static unsigned long dirty_freerun_ceiling(unsigned long thresh,
unsigned long bg_thresh)
{
return (thresh + bg_thresh) / 2;
}
static unsigned long hard_dirty_limit(unsigned long thresh)
{
return max(thresh, global_dirty_limit);
@ -497,6 +449,198 @@ unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
return bdi_dirty;
}
/*
* Dirty position control.
*
* (o) global/bdi setpoints
*
* We want the dirty pages be balanced around the global/bdi setpoints.
* When the number of dirty pages is higher/lower than the setpoint, the
* dirty position control ratio (and hence task dirty ratelimit) will be
* decreased/increased to bring the dirty pages back to the setpoint.
*
* pos_ratio = 1 << RATELIMIT_CALC_SHIFT
*
* if (dirty < setpoint) scale up pos_ratio
* if (dirty > setpoint) scale down pos_ratio
*
* if (bdi_dirty < bdi_setpoint) scale up pos_ratio
* if (bdi_dirty > bdi_setpoint) scale down pos_ratio
*
* task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT
*
* (o) global control line
*
* ^ pos_ratio
* |
* | |<===== global dirty control scope ======>|
* 2.0 .............*
* | .*
* | . *
* | . *
* | . *
* | . *
* | . *
* 1.0 ................................*
* | . . *
* | . . *
* | . . *
* | . . *
* | . . *
* 0 +------------.------------------.----------------------*------------->
* freerun^ setpoint^ limit^ dirty pages
*
* (o) bdi control line
*
* ^ pos_ratio
* |
* | *
* | *
* | *
* | *
* | * |<=========== span ============>|
* 1.0 .......................*
* | . *
* | . *
* | . *
* | . *
* | . *
* | . *
* | . *
* | . *
* | . *
* | . *
* | . *
* 1/4 ...............................................* * * * * * * * * * * *
* | . .
* | . .
* | . .
* 0 +----------------------.-------------------------------.------------->
* bdi_setpoint^ x_intercept^
*
* The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can
* be smoothly throttled down to normal if it starts high in situations like
* - start writing to a slow SD card and a fast disk at the same time. The SD
* card's bdi_dirty may rush to many times higher than bdi_setpoint.
* - the bdi dirty thresh drops quickly due to change of JBOD workload
*/
static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
unsigned long bdi_thresh,
unsigned long bdi_dirty)
{
unsigned long write_bw = bdi->avg_write_bandwidth;
unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
unsigned long limit = hard_dirty_limit(thresh);
unsigned long x_intercept;
unsigned long setpoint; /* dirty pages' target balance point */
unsigned long bdi_setpoint;
unsigned long span;
long long pos_ratio; /* for scaling up/down the rate limit */
long x;
if (unlikely(dirty >= limit))
return 0;
/*
* global setpoint
*
* setpoint - dirty 3
* f(dirty) := 1.0 + (----------------)
* limit - setpoint
*
* it's a 3rd order polynomial that subjects to
*
* (1) f(freerun) = 2.0 => rampup dirty_ratelimit reasonably fast
* (2) f(setpoint) = 1.0 => the balance point
* (3) f(limit) = 0 => the hard limit
* (4) df/dx <= 0 => negative feedback control
* (5) the closer to setpoint, the smaller |df/dx| (and the reverse)
* => fast response on large errors; small oscillation near setpoint
*/
setpoint = (freerun + limit) / 2;
x = div_s64((setpoint - dirty) << RATELIMIT_CALC_SHIFT,
limit - setpoint + 1);
pos_ratio = x;
pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT;
pos_ratio += 1 << RATELIMIT_CALC_SHIFT;
/*
* We have computed basic pos_ratio above based on global situation. If
* the bdi is over/under its share of dirty pages, we want to scale
* pos_ratio further down/up. That is done by the following mechanism.
*/
/*
* bdi setpoint
*
* f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint)
*
* x_intercept - bdi_dirty
* := --------------------------
* x_intercept - bdi_setpoint
*
* The main bdi control line is a linear function that subjects to
*
* (1) f(bdi_setpoint) = 1.0
* (2) k = - 1 / (8 * write_bw) (in single bdi case)
* or equally: x_intercept = bdi_setpoint + 8 * write_bw
*
* For single bdi case, the dirty pages are observed to fluctuate
* regularly within range
* [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2]
* for various filesystems, where (2) can yield in a reasonable 12.5%
* fluctuation range for pos_ratio.
*
* For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its
* own size, so move the slope over accordingly and choose a slope that
* yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh.
*/
if (unlikely(bdi_thresh > thresh))
bdi_thresh = thresh;
bdi_thresh = max(bdi_thresh, (limit - dirty) / 8);
/*
* scale global setpoint to bdi's:
* bdi_setpoint = setpoint * bdi_thresh / thresh
*/
x = div_u64((u64)bdi_thresh << 16, thresh + 1);
bdi_setpoint = setpoint * (u64)x >> 16;
/*
* Use span=(8*write_bw) in single bdi case as indicated by
* (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case.
*
* bdi_thresh thresh - bdi_thresh
* span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh
* thresh thresh
*/
span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16;
x_intercept = bdi_setpoint + span;
if (bdi_dirty < x_intercept - span / 4) {
pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty),
x_intercept - bdi_setpoint + 1);
} else
pos_ratio /= 4;
/*
* bdi reserve area, safeguard against dirty pool underrun and disk idle
* It may push the desired control point of global dirty pages higher
* than setpoint.
*/
x_intercept = bdi_thresh / 2;
if (bdi_dirty < x_intercept) {
if (bdi_dirty > x_intercept / 8)
pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty);
else
pos_ratio *= 8;
}
return pos_ratio;
}
static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
unsigned long elapsed,
unsigned long written)
@ -593,8 +737,153 @@ static void global_update_bandwidth(unsigned long thresh,
spin_unlock(&dirty_lock);
}
/*
* Maintain bdi->dirty_ratelimit, the base dirty throttle rate.
*
* Normal bdi tasks will be curbed at or below it in long term.
* Obviously it should be around (write_bw / N) when there are N dd tasks.
*/
static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
unsigned long bdi_thresh,
unsigned long bdi_dirty,
unsigned long dirtied,
unsigned long elapsed)
{
unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
unsigned long limit = hard_dirty_limit(thresh);
unsigned long setpoint = (freerun + limit) / 2;
unsigned long write_bw = bdi->avg_write_bandwidth;
unsigned long dirty_ratelimit = bdi->dirty_ratelimit;
unsigned long dirty_rate;
unsigned long task_ratelimit;
unsigned long balanced_dirty_ratelimit;
unsigned long pos_ratio;
unsigned long step;
unsigned long x;
/*
* The dirty rate will match the writeout rate in long term, except
* when dirty pages are truncated by userspace or re-dirtied by FS.
*/
dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed;
pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty,
bdi_thresh, bdi_dirty);
/*
* task_ratelimit reflects each dd's dirty rate for the past 200ms.
*/
task_ratelimit = (u64)dirty_ratelimit *
pos_ratio >> RATELIMIT_CALC_SHIFT;
task_ratelimit++; /* it helps rampup dirty_ratelimit from tiny values */
/*
* A linear estimation of the "balanced" throttle rate. The theory is,
* if there are N dd tasks, each throttled at task_ratelimit, the bdi's
* dirty_rate will be measured to be (N * task_ratelimit). So the below
* formula will yield the balanced rate limit (write_bw / N).
*
* Note that the expanded form is not a pure rate feedback:
* rate_(i+1) = rate_(i) * (write_bw / dirty_rate) (1)
* but also takes pos_ratio into account:
* rate_(i+1) = rate_(i) * (write_bw / dirty_rate) * pos_ratio (2)
*
* (1) is not realistic because pos_ratio also takes part in balancing
* the dirty rate. Consider the state
* pos_ratio = 0.5 (3)
* rate = 2 * (write_bw / N) (4)
* If (1) is used, it will stuck in that state! Because each dd will
* be throttled at
* task_ratelimit = pos_ratio * rate = (write_bw / N) (5)
* yielding
* dirty_rate = N * task_ratelimit = write_bw (6)
* put (6) into (1) we get
* rate_(i+1) = rate_(i) (7)
*
* So we end up using (2) to always keep
* rate_(i+1) ~= (write_bw / N) (8)
* regardless of the value of pos_ratio. As long as (8) is satisfied,
* pos_ratio is able to drive itself to 1.0, which is not only where
* the dirty count meet the setpoint, but also where the slope of
* pos_ratio is most flat and hence task_ratelimit is least fluctuated.
*/
balanced_dirty_ratelimit = div_u64((u64)task_ratelimit * write_bw,
dirty_rate | 1);
/*
* We could safely do this and return immediately:
*
* bdi->dirty_ratelimit = balanced_dirty_ratelimit;
*
* However to get a more stable dirty_ratelimit, the below elaborated
* code makes use of task_ratelimit to filter out sigular points and
* limit the step size.
*
* The below code essentially only uses the relative value of
*
* task_ratelimit - dirty_ratelimit
* = (pos_ratio - 1) * dirty_ratelimit
*
* which reflects the direction and size of dirty position error.
*/
/*
* dirty_ratelimit will follow balanced_dirty_ratelimit iff
* task_ratelimit is on the same side of dirty_ratelimit, too.
* For example, when
* - dirty_ratelimit > balanced_dirty_ratelimit
* - dirty_ratelimit > task_ratelimit (dirty pages are above setpoint)
* lowering dirty_ratelimit will help meet both the position and rate
* control targets. Otherwise, don't update dirty_ratelimit if it will
* only help meet the rate target. After all, what the users ultimately
* feel and care are stable dirty rate and small position error.
*
* |task_ratelimit - dirty_ratelimit| is used to limit the step size
* and filter out the sigular points of balanced_dirty_ratelimit. Which
* keeps jumping around randomly and can even leap far away at times
* due to the small 200ms estimation period of dirty_rate (we want to
* keep that period small to reduce time lags).
*/
step = 0;
if (dirty < setpoint) {
x = min(bdi->balanced_dirty_ratelimit,
min(balanced_dirty_ratelimit, task_ratelimit));
if (dirty_ratelimit < x)
step = x - dirty_ratelimit;
} else {
x = max(bdi->balanced_dirty_ratelimit,
max(balanced_dirty_ratelimit, task_ratelimit));
if (dirty_ratelimit > x)
step = dirty_ratelimit - x;
}
/*
* Don't pursue 100% rate matching. It's impossible since the balanced
* rate itself is constantly fluctuating. So decrease the track speed
* when it gets close to the target. Helps eliminate pointless tremors.
*/
step >>= dirty_ratelimit / (2 * step + 1);
/*
* Limit the tracking speed to avoid overshooting.
*/
step = (step + 7) / 8;
if (dirty_ratelimit < balanced_dirty_ratelimit)
dirty_ratelimit += step;
else
dirty_ratelimit -= step;
bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit);
}
void __bdi_update_bandwidth(struct backing_dev_info *bdi,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
unsigned long bdi_thresh,
unsigned long bdi_dirty,
@ -602,6 +891,7 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi,
{
unsigned long now = jiffies;
unsigned long elapsed = now - bdi->bw_time_stamp;
unsigned long dirtied;
unsigned long written;
/*
@ -610,6 +900,7 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi,
if (elapsed < BANDWIDTH_INTERVAL)
return;
dirtied = percpu_counter_read(&bdi->bdi_stat[BDI_DIRTIED]);
written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
/*
@ -619,18 +910,23 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi,
if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
goto snapshot;
if (thresh)
if (thresh) {
global_update_bandwidth(thresh, dirty, now);
bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty,
bdi_thresh, bdi_dirty,
dirtied, elapsed);
}
bdi_update_write_bandwidth(bdi, elapsed, written);
snapshot:
bdi->dirtied_stamp = dirtied;
bdi->written_stamp = written;
bdi->bw_time_stamp = now;
}
static void bdi_update_bandwidth(struct backing_dev_info *bdi,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
unsigned long bdi_thresh,
unsigned long bdi_dirty,
@ -639,37 +935,99 @@ static void bdi_update_bandwidth(struct backing_dev_info *bdi,
if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
return;
spin_lock(&bdi->wb.list_lock);
__bdi_update_bandwidth(bdi, thresh, dirty, bdi_thresh, bdi_dirty,
start_time);
__bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty,
bdi_thresh, bdi_dirty, start_time);
spin_unlock(&bdi->wb.list_lock);
}
/*
* After a task dirtied this many pages, balance_dirty_pages_ratelimited_nr()
* will look to see if it needs to start dirty throttling.
*
* If dirty_poll_interval is too low, big NUMA machines will call the expensive
* global_page_state() too often. So scale it near-sqrt to the safety margin
* (the number of pages we may dirty without exceeding the dirty limits).
*/
static unsigned long dirty_poll_interval(unsigned long dirty,
unsigned long thresh)
{
if (thresh > dirty)
return 1UL << (ilog2(thresh - dirty) >> 1);
return 1;
}
static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
unsigned long bdi_dirty)
{
unsigned long bw = bdi->avg_write_bandwidth;
unsigned long hi = ilog2(bw);
unsigned long lo = ilog2(bdi->dirty_ratelimit);
unsigned long t;
/* target for 20ms max pause on 1-dd case */
t = HZ / 50;
/*
* Scale up pause time for concurrent dirtiers in order to reduce CPU
* overheads.
*
* (N * 20ms) on 2^N concurrent tasks.
*/
if (hi > lo)
t += (hi - lo) * (20 * HZ) / 1024;
/*
* Limit pause time for small memory systems. If sleeping for too long
* time, a small pool of dirty/writeback pages may go empty and disk go
* idle.
*
* 8 serves as the safety ratio.
*/
if (bdi_dirty)
t = min(t, bdi_dirty * HZ / (8 * bw + 1));
/*
* The pause time will be settled within range (max_pause/4, max_pause).
* Apply a minimal value of 4 to get a non-zero max_pause/4.
*/
return clamp_val(t, 4, MAX_PAUSE);
}
/*
* balance_dirty_pages() must be called by processes which are generating dirty
* data. It looks at the number of dirty pages in the machine and will force
* the caller to perform writeback if the system is over `vm_dirty_ratio'.
* the caller to wait once crossing the (background_thresh + dirty_thresh) / 2.
* If we're over `background_thresh' then the writeback threads are woken to
* perform some writeout.
*/
static void balance_dirty_pages(struct address_space *mapping,
unsigned long write_chunk)
unsigned long pages_dirtied)
{
unsigned long nr_reclaimable, bdi_nr_reclaimable;
unsigned long nr_reclaimable; /* = file_dirty + unstable_nfs */
unsigned long bdi_reclaimable;
unsigned long nr_dirty; /* = file_dirty + writeback + unstable_nfs */
unsigned long bdi_dirty;
unsigned long freerun;
unsigned long background_thresh;
unsigned long dirty_thresh;
unsigned long bdi_thresh;
unsigned long task_bdi_thresh;
unsigned long min_task_bdi_thresh;
unsigned long pages_written = 0;
unsigned long pause = 1;
long pause = 0;
long uninitialized_var(max_pause);
bool dirty_exceeded = false;
bool clear_dirty_exceeded = true;
unsigned long task_ratelimit;
unsigned long uninitialized_var(dirty_ratelimit);
unsigned long pos_ratio;
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long start_time = jiffies;
for (;;) {
/*
* Unstable writes are a feature of certain networked
* filesystems (i.e. NFS) in which data may have been
* written to the server's write cache, but has not yet
* been flushed to permanent storage.
*/
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
@ -681,12 +1039,28 @@ static void balance_dirty_pages(struct address_space *mapping,
* catch-up. This avoids (excessively) small writeouts
* when the bdi limits are ramping up.
*/
if (nr_dirty <= (background_thresh + dirty_thresh) / 2)
freerun = dirty_freerun_ceiling(dirty_thresh,
background_thresh);
if (nr_dirty <= freerun)
break;
if (unlikely(!writeback_in_progress(bdi)))
bdi_start_background_writeback(bdi);
/*
* bdi_thresh is not treated as some limiting factor as
* dirty_thresh, due to reasons
* - in JBOD setup, bdi_thresh can fluctuate a lot
* - in a system with HDD and USB key, the USB key may somehow
* go into state (bdi_dirty >> bdi_thresh) either because
* bdi_dirty starts high, or because bdi_thresh drops low.
* In this case we don't want to hard throttle the USB key
* dirtiers for 100 seconds until bdi_dirty drops under
* bdi_thresh. Instead the auxiliary bdi control line in
* bdi_position_ratio() will let the dirtier task progress
* at some rate <= (write_bw / 2) for bringing down bdi_dirty.
*/
bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
min_task_bdi_thresh = task_min_dirty_limit(bdi_thresh);
task_bdi_thresh = task_dirty_limit(current, bdi_thresh);
/*
* In order to avoid the stacked BDI deadlock we need
@ -698,56 +1072,69 @@ static void balance_dirty_pages(struct address_space *mapping,
* actually dirty; with m+n sitting in the percpu
* deltas.
*/
if (task_bdi_thresh < 2 * bdi_stat_error(bdi)) {
bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
bdi_dirty = bdi_nr_reclaimable +
if (bdi_thresh < 2 * bdi_stat_error(bdi)) {
bdi_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
bdi_dirty = bdi_reclaimable +
bdi_stat_sum(bdi, BDI_WRITEBACK);
} else {
bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
bdi_dirty = bdi_nr_reclaimable +
bdi_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
bdi_dirty = bdi_reclaimable +
bdi_stat(bdi, BDI_WRITEBACK);
}
/*
* The bdi thresh is somehow "soft" limit derived from the
* global "hard" limit. The former helps to prevent heavy IO
* bdi or process from holding back light ones; The latter is
* the last resort safeguard.
*/
dirty_exceeded = (bdi_dirty > task_bdi_thresh) ||
dirty_exceeded = (bdi_dirty > bdi_thresh) ||
(nr_dirty > dirty_thresh);
clear_dirty_exceeded = (bdi_dirty <= min_task_bdi_thresh) &&
(nr_dirty <= dirty_thresh);
if (!dirty_exceeded)
break;
if (!bdi->dirty_exceeded)
if (dirty_exceeded && !bdi->dirty_exceeded)
bdi->dirty_exceeded = 1;
bdi_update_bandwidth(bdi, dirty_thresh, nr_dirty,
bdi_thresh, bdi_dirty, start_time);
bdi_update_bandwidth(bdi, dirty_thresh, background_thresh,
nr_dirty, bdi_thresh, bdi_dirty,
start_time);
/* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
* Unstable writes are a feature of certain networked
* filesystems (i.e. NFS) in which data may have been
* written to the server's write cache, but has not yet
* been flushed to permanent storage.
* Only move pages to writeback if this bdi is over its
* threshold otherwise wait until the disk writes catch
* up.
*/
trace_balance_dirty_start(bdi);
if (bdi_nr_reclaimable > task_bdi_thresh) {
pages_written += writeback_inodes_wb(&bdi->wb,
write_chunk);
trace_balance_dirty_written(bdi, pages_written);
if (pages_written >= write_chunk)
break; /* We've done our duty */
max_pause = bdi_max_pause(bdi, bdi_dirty);
dirty_ratelimit = bdi->dirty_ratelimit;
pos_ratio = bdi_position_ratio(bdi, dirty_thresh,
background_thresh, nr_dirty,
bdi_thresh, bdi_dirty);
if (unlikely(pos_ratio == 0)) {
pause = max_pause;
goto pause;
}
task_ratelimit = (u64)dirty_ratelimit *
pos_ratio >> RATELIMIT_CALC_SHIFT;
pause = (HZ * pages_dirtied) / (task_ratelimit | 1);
if (unlikely(pause <= 0)) {
trace_balance_dirty_pages(bdi,
dirty_thresh,
background_thresh,
nr_dirty,
bdi_thresh,
bdi_dirty,
dirty_ratelimit,
task_ratelimit,
pages_dirtied,
pause,
start_time);
pause = 1; /* avoid resetting nr_dirtied_pause below */
break;
}
pause = min(pause, max_pause);
pause:
trace_balance_dirty_pages(bdi,
dirty_thresh,
background_thresh,
nr_dirty,
bdi_thresh,
bdi_dirty,
dirty_ratelimit,
task_ratelimit,
pages_dirtied,
pause,
start_time);
__set_current_state(TASK_UNINTERRUPTIBLE);
io_schedule_timeout(pause);
trace_balance_dirty_wait(bdi);
dirty_thresh = hard_dirty_limit(dirty_thresh);
/*
@ -756,24 +1143,30 @@ static void balance_dirty_pages(struct address_space *mapping,
* 200ms is typically more than enough to curb heavy dirtiers;
* (b) the pause time limit makes the dirtiers more responsive.
*/
if (nr_dirty < dirty_thresh &&
bdi_dirty < (task_bdi_thresh + bdi_thresh) / 2 &&
time_after(jiffies, start_time + MAX_PAUSE))
if (nr_dirty < dirty_thresh)
break;
/*
* Increase the delay for each loop, up to our previous
* default of taking a 100ms nap.
*/
pause <<= 1;
if (pause > HZ / 10)
pause = HZ / 10;
}
/* Clear dirty_exceeded flag only when no task can exceed the limit */
if (clear_dirty_exceeded && bdi->dirty_exceeded)
if (!dirty_exceeded && bdi->dirty_exceeded)
bdi->dirty_exceeded = 0;
current->nr_dirtied = 0;
if (pause == 0) { /* in freerun area */
current->nr_dirtied_pause =
dirty_poll_interval(nr_dirty, dirty_thresh);
} else if (pause <= max_pause / 4 &&
pages_dirtied >= current->nr_dirtied_pause) {
current->nr_dirtied_pause = clamp_val(
dirty_ratelimit * (max_pause / 2) / HZ,
pages_dirtied + pages_dirtied / 8,
pages_dirtied * 4);
} else if (pause >= max_pause) {
current->nr_dirtied_pause = 1 | clamp_val(
dirty_ratelimit * (max_pause / 2) / HZ,
pages_dirtied / 4,
pages_dirtied - pages_dirtied / 8);
}
if (writeback_in_progress(bdi))
return;
@ -785,8 +1178,10 @@ static void balance_dirty_pages(struct address_space *mapping,
* In normal mode, we start background writeout at the lower
* background_thresh, to keep the amount of dirty memory low.
*/
if ((laptop_mode && pages_written) ||
(!laptop_mode && (nr_reclaimable > background_thresh)))
if (laptop_mode)
return;
if (nr_reclaimable > background_thresh)
bdi_start_background_writeback(bdi);
}
@ -800,7 +1195,7 @@ void set_page_dirty_balance(struct page *page, int page_mkwrite)
}
}
static DEFINE_PER_CPU(unsigned long, bdp_ratelimits) = 0;
static DEFINE_PER_CPU(int, bdp_ratelimits);
/**
* balance_dirty_pages_ratelimited_nr - balance dirty memory state
@ -820,31 +1215,39 @@ void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
unsigned long nr_pages_dirtied)
{
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long ratelimit;
unsigned long *p;
int ratelimit;
int *p;
if (!bdi_cap_account_dirty(bdi))
return;
ratelimit = ratelimit_pages;
if (mapping->backing_dev_info->dirty_exceeded)
ratelimit = 8;
ratelimit = current->nr_dirtied_pause;
if (bdi->dirty_exceeded)
ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));
current->nr_dirtied += nr_pages_dirtied;
/*
* Check the rate limiting. Also, we do not want to throttle real-time
* tasks in balance_dirty_pages(). Period.
*/
preempt_disable();
/*
* This prevents one CPU to accumulate too many dirtied pages without
* calling into balance_dirty_pages(), which can happen when there are
* 1000+ tasks, all of them start dirtying pages at exactly the same
* time, hence all honoured too large initial task->nr_dirtied_pause.
*/
p = &__get_cpu_var(bdp_ratelimits);
*p += nr_pages_dirtied;
if (unlikely(*p >= ratelimit)) {
ratelimit = sync_writeback_pages(*p);
if (unlikely(current->nr_dirtied >= ratelimit))
*p = 0;
preempt_enable();
balance_dirty_pages(mapping, ratelimit);
return;
else {
*p += nr_pages_dirtied;
if (unlikely(*p >= ratelimit_pages)) {
*p = 0;
ratelimit = 0;
}
}
preempt_enable();
if (unlikely(current->nr_dirtied >= ratelimit))
balance_dirty_pages(mapping, current->nr_dirtied);
}
EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
@ -900,7 +1303,8 @@ void laptop_mode_timer_fn(unsigned long data)
* threshold
*/
if (bdi_has_dirty_io(&q->backing_dev_info))
bdi_start_writeback(&q->backing_dev_info, nr_pages);
bdi_start_writeback(&q->backing_dev_info, nr_pages,
WB_REASON_LAPTOP_TIMER);
}
/*
@ -939,22 +1343,17 @@ void laptop_sync_completion(void)
*
* Here we set ratelimit_pages to a level which ensures that when all CPUs are
* dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
* thresholds before writeback cuts in.
*
* But the limit should not be set too high. Because it also controls the
* amount of memory which the balance_dirty_pages() caller has to write back.
* If this is too large then the caller will block on the IO queue all the
* time. So limit it to four megabytes - the balance_dirty_pages() caller
* will write six megabyte chunks, max.
* thresholds.
*/
void writeback_set_ratelimit(void)
{
ratelimit_pages = vm_total_pages / (num_online_cpus() * 32);
unsigned long background_thresh;
unsigned long dirty_thresh;
global_dirty_limits(&background_thresh, &dirty_thresh);
ratelimit_pages = dirty_thresh / (num_online_cpus() * 32);
if (ratelimit_pages < 16)
ratelimit_pages = 16;
if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
}
static int __cpuinit
@ -1324,6 +1723,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
__inc_zone_page_state(page, NR_FILE_DIRTY);
__inc_zone_page_state(page, NR_DIRTIED);
__inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
__inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED);
task_dirty_inc(current);
task_io_account_write(PAGE_CACHE_SIZE);
}

3
mm/vmscan.c
View file

@ -2266,7 +2266,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
*/
writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
if (total_scanned > writeback_threshold) {
wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
WB_REASON_TRY_TO_FREE_PAGES);
sc->may_writepage = 1;
}