fs: use fast counters for vfs caches
percpu_counter library generates quite nasty code, so unless you need
to dynamically allocate counters or take fast approximate value, a
simple per cpu set of counters is much better.
The percpu_counter can never be made to work as well, because it has an
indirection from pointer to percpu memory, and it can't use direct
this_cpu_inc interfaces because it doesn't use static PER_CPU data, so
code will always be worse.
In the fastpath, it is the difference between this:
incl %gs:nr_dentry # nr_dentry
and this:
movl percpu_counter_batch(%rip), %edx # percpu_counter_batch,
movl $1, %esi #,
movq $nr_dentry, %rdi #,
call __percpu_counter_add # (plus I clobber registers)
__percpu_counter_add:
pushq %rbp #
movq %rsp, %rbp #,
subq $32, %rsp #,
movq %rbx, -24(%rbp) #,
movq %r12, -16(%rbp) #,
movq %r13, -8(%rbp) #,
movq %rdi, %rbx # fbc, fbc
#APP
# 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1
movq %gs:kernel_stack,%rax #, pfo_ret__
# 0 "" 2
#NO_APP
incl -8124(%rax) # <variable>.preempt_count
movq 32(%rdi), %r12 # <variable>.counters, tcp_ptr__
#APP
# 78 "lib/percpu_counter.c" 1
add %gs:this_cpu_off, %r12 # this_cpu_off, tcp_ptr__
# 0 "" 2
#NO_APP
movslq (%r12),%r13 #* tcp_ptr__, tmp73
movslq %edx,%rax # batch, batch
addq %rsi, %r13 # amount, count
cmpq %rax, %r13 # batch, count
jge .L27 #,
negl %edx # tmp76
movslq %edx,%rdx # tmp76, tmp77
cmpq %rdx, %r13 # tmp77, count
jg .L28 #,
.L27:
movq %rbx, %rdi # fbc,
call _raw_spin_lock #
addq %r13, 8(%rbx) # count, <variable>.count
movq %rbx, %rdi # fbc,
movl $0, (%r12) #,* tcp_ptr__
call _raw_spin_unlock #
.L29:
#APP
# 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1
movq %gs:kernel_stack,%rax #, pfo_ret__
# 0 "" 2
#NO_APP
decl -8124(%rax) # <variable>.preempt_count
movq -8136(%rax), %rax #, D.14625
testb $8, %al #, D.14625
jne .L32 #,
.L31:
movq -24(%rbp), %rbx #,
movq -16(%rbp), %r12 #,
movq -8(%rbp), %r13 #,
leave
ret
.p2align 4,,10
.p2align 3
.L28:
movl %r13d, (%r12) # count,*
jmp .L29 #
.L32:
call preempt_schedule #
.p2align 4,,6
jmp .L31 #
.size __percpu_counter_add, .-__percpu_counter_add
.p2align 4,,15
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin
parent
86c8749ede
commit
3e880fb5e4
2 changed files with 23 additions and 13 deletions
19
fs/dcache.c
19
fs/dcache.c
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@ -67,13 +67,22 @@ struct dentry_stat_t dentry_stat = {
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.age_limit = 45,
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};
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static struct percpu_counter nr_dentry __cacheline_aligned_in_smp;
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static DEFINE_PER_CPU(unsigned int, nr_dentry);
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
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static int get_nr_dentry(void)
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{
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int i;
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int sum = 0;
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for_each_possible_cpu(i)
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sum += per_cpu(nr_dentry, i);
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return sum < 0 ? 0 : sum;
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}
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int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
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size_t *lenp, loff_t *ppos)
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{
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dentry_stat.nr_dentry = percpu_counter_sum_positive(&nr_dentry);
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dentry_stat.nr_dentry = get_nr_dentry();
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return proc_dointvec(table, write, buffer, lenp, ppos);
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}
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#endif
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@ -93,7 +102,7 @@ static void __d_free(struct rcu_head *head)
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*/
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static void d_free(struct dentry *dentry)
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{
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percpu_counter_dec(&nr_dentry);
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this_cpu_dec(nr_dentry);
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if (dentry->d_op && dentry->d_op->d_release)
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dentry->d_op->d_release(dentry);
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@ -981,7 +990,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
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list_add(&dentry->d_u.d_child, &parent->d_subdirs);
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spin_unlock(&dcache_lock);
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percpu_counter_inc(&nr_dentry);
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this_cpu_inc(nr_dentry);
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return dentry;
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}
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@ -2418,8 +2427,6 @@ static void __init dcache_init(void)
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{
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int loop;
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percpu_counter_init(&nr_dentry, 0);
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/*
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* A constructor could be added for stable state like the lists,
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* but it is probably not worth it because of the cache nature
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17
fs/inode.c
17
fs/inode.c
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@ -102,13 +102,17 @@ static DECLARE_RWSEM(iprune_sem);
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*/
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struct inodes_stat_t inodes_stat;
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static struct percpu_counter nr_inodes __cacheline_aligned_in_smp;
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static DEFINE_PER_CPU(unsigned int, nr_inodes);
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static struct kmem_cache *inode_cachep __read_mostly;
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static inline int get_nr_inodes(void)
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static int get_nr_inodes(void)
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{
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return percpu_counter_sum_positive(&nr_inodes);
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int i;
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int sum = 0;
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for_each_possible_cpu(i)
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sum += per_cpu(nr_inodes, i);
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return sum < 0 ? 0 : sum;
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}
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static inline int get_nr_inodes_unused(void)
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@ -118,9 +122,9 @@ static inline int get_nr_inodes_unused(void)
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int get_nr_dirty_inodes(void)
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{
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/* not actually dirty inodes, but a wild approximation */
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int nr_dirty = get_nr_inodes() - get_nr_inodes_unused();
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return nr_dirty > 0 ? nr_dirty : 0;
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}
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/*
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@ -222,7 +226,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
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inode->i_fsnotify_mask = 0;
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#endif
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percpu_counter_inc(&nr_inodes);
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this_cpu_inc(nr_inodes);
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return 0;
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out:
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@ -264,7 +268,7 @@ void __destroy_inode(struct inode *inode)
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if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
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posix_acl_release(inode->i_default_acl);
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#endif
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percpu_counter_dec(&nr_inodes);
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this_cpu_dec(nr_inodes);
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}
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EXPORT_SYMBOL(__destroy_inode);
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@ -1646,7 +1650,6 @@ void __init inode_init(void)
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SLAB_MEM_SPREAD),
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init_once);
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register_shrinker(&icache_shrinker);
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percpu_counter_init(&nr_inodes, 0);
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/* Hash may have been set up in inode_init_early */
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if (!hashdist)
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