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mm, swap: add sysfs interface for VMA based swap readahead

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The sysfs interface to control the VMA based swap readahead is added as
follow,

/sys/kernel/mm/swap/vma_ra_enabled

Enable the VMA based swap readahead algorithm, or use the original
global swap readahead algorithm.

/sys/kernel/mm/swap/vma_ra_max_order

Set the max order of the readahead window size for the VMA based swap
readahead algorithm.

The corresponding ABI documentation is added too.

Link: http://lkml.kernel.org/r/20170807054038.1843-5-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Huang Ying 2017-09-06 16:24:40 -07:00 committed by Linus Torvalds
parent ec560175c0
commit d9bfcfdc41
2 changed files with 106 additions and 0 deletions
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26
Documentation/ABI/testing/sysfs-kernel-mm-swap Normal file
View file

@ -0,0 +1,26 @@
What: /sys/kernel/mm/swap/
Date: August 2017
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: Interface for swapping
What: /sys/kernel/mm/swap/vma_ra_enabled
Date: August 2017
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: Enable/disable VMA based swap readahead.
If set to true, the VMA based swap readahead algorithm
will be used for swappable anonymous pages mapped in a
VMA, and the global swap readahead algorithm will be
still used for tmpfs etc. other users. If set to
false, the global swap readahead algorithm will be
used for all swappable pages.
What: /sys/kernel/mm/swap/vma_ra_max_order
Date: August 2017
Contact: Linux memory management mailing list <linux-mm@kvack.org>
Description: The max readahead size in order for VMA based swap readahead
VMA based swap readahead algorithm will readahead at
most 1 << max_order pages for each readahead. The
real readahead size for each readahead will be scaled
according to the estimation algorithm.

80
mm/swap_state.c
View file

@ -751,3 +751,83 @@ struct page *do_swap_page_readahead(swp_entry_t fentry, gfp_t gfp_mask,
return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
swap_ra->win == 1);
}
#ifdef CONFIG_SYSFS
static ssize_t vma_ra_enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%s\n", swap_vma_readahead ? "true" : "false");
}
static ssize_t vma_ra_enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
swap_vma_readahead = true;
else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
swap_vma_readahead = false;
else
return -EINVAL;
return count;
}
static struct kobj_attribute vma_ra_enabled_attr =
__ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
vma_ra_enabled_store);
static ssize_t vma_ra_max_order_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%d\n", swap_ra_max_order);
}
static ssize_t vma_ra_max_order_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err, v;
err = kstrtoint(buf, 10, &v);
if (err || v > SWAP_RA_ORDER_CEILING || v <= 0)
return -EINVAL;
swap_ra_max_order = v;
return count;
}
static struct kobj_attribute vma_ra_max_order_attr =
__ATTR(vma_ra_max_order, 0644, vma_ra_max_order_show,
vma_ra_max_order_store);
static struct attribute *swap_attrs[] = {
&vma_ra_enabled_attr.attr,
&vma_ra_max_order_attr.attr,
NULL,
};
static struct attribute_group swap_attr_group = {
.attrs = swap_attrs,
};
static int __init swap_init_sysfs(void)
{
int err;
struct kobject *swap_kobj;
swap_kobj = kobject_create_and_add("swap", mm_kobj);
if (!swap_kobj) {
pr_err("failed to create swap kobject\n");
return -ENOMEM;
}
err = sysfs_create_group(swap_kobj, &swap_attr_group);
if (err) {
pr_err("failed to register swap group\n");
goto delete_obj;
}
return 0;
delete_obj:
kobject_put(swap_kobj);
return err;
}
subsys_initcall(swap_init_sysfs);
#endif