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mm/ksm: add pages scanned metric 

ksm currently maintains several statistics, which let you determine how
successful KSM is at sharing pages.  However it does not contain a metric
to determine how much work it does.

This commit adds the pages scanned metric.  This allows the administrator
to determine how many pages have been scanned over a period of time.

Link: https://lkml.kernel.org/r/20230811193655.2518943-1-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Stefan Roesch 2023-08-11 12:36:55 -07:00 committed by Andrew Morton
parent 0790e1e2b1
commit b348b5fe2b
2 changed files with 17 additions and 1 deletions
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2
Documentation/admin-guide/mm/ksm.rst
View File

@ -159,6 +159,8 @@ The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
general_profit
how effective is KSM. The calculation is explained below.
pages_scanned
how many pages are being scanned for ksm
pages_shared
how many shared pages are being used
pages_sharing

16
mm/ksm.c
View File

@ -242,6 +242,9 @@ static struct kmem_cache *rmap_item_cache;
static struct kmem_cache *stable_node_cache;
static struct kmem_cache *mm_slot_cache;
/* The number of pages scanned */
static unsigned long ksm_pages_scanned;
/* The number of nodes in the stable tree */
static unsigned long ksm_pages_shared;
@ -2476,8 +2479,9 @@ static void ksm_do_scan(unsigned int scan_npages)
{
struct ksm_rmap_item *rmap_item;
struct page *page;
unsigned int npages = scan_npages;
while (scan_npages-- && likely(!freezing(current))) {
while (npages-- && likely(!freezing(current))) {
cond_resched();
rmap_item = scan_get_next_rmap_item(&page);
if (!rmap_item)
@ -2485,6 +2489,8 @@ static void ksm_do_scan(unsigned int scan_npages)
cmp_and_merge_page(page, rmap_item);
put_page(page);
}
ksm_pages_scanned += scan_npages - npages;
}
static int ksmd_should_run(void)
@ -3323,6 +3329,13 @@ static ssize_t max_page_sharing_store(struct kobject *kobj,
}
KSM_ATTR(max_page_sharing);
static ssize_t pages_scanned_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sysfs_emit(buf, "%lu\n", ksm_pages_scanned);
}
KSM_ATTR_RO(pages_scanned);
static ssize_t pages_shared_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
@ -3431,6 +3444,7 @@ static struct attribute *ksm_attrs[] = {
&sleep_millisecs_attr.attr,
&pages_to_scan_attr.attr,
&run_attr.attr,
&pages_scanned_attr.attr,
&pages_shared_attr.attr,
&pages_sharing_attr.attr,
&pages_unshared_attr.attr,