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proc: export idle flag via kpageflags

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As noted by Minchan, a benefit of reading idle flag from /proc/kpageflags
is that one can easily filter dirty and/or unevictable pages while
estimating the size of unused memory.

Note that idle flag read from /proc/kpageflags may be stale in case the
page was accessed via a PTE, because it would be too costly to iterate
over all page mappings on each /proc/kpageflags read to provide an
up-to-date value.  To make sure the flag is up-to-date one has to read
/sys/kernel/mm/page_idle/bitmap first.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Reviewed-by: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vladimir Davydov 2015-09-09 15:35:48 -07:00 committed by Linus Torvalds
parent 33c3fc71c8
commit f074a8f49e
3 changed files with 11 additions and 0 deletions
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7
Documentation/vm/pagemap.txt
View File

@ -70,6 +70,7 @@ There are four components to pagemap:
22. THP
23. BALLOON
24. ZERO_PAGE
25. IDLE
* /proc/kpagecgroup. This file contains a 64-bit inode number of the
memory cgroup each page is charged to, indexed by PFN. Only available when
@ -120,6 +121,12 @@ Short descriptions to the page flags:
24. ZERO_PAGE
zero page for pfn_zero or huge_zero page
25. IDLE
page has not been accessed since it was marked idle (see
Documentation/vm/idle_page_tracking.txt). Note that this flag may be
stale in case the page was accessed via a PTE. To make sure the flag
is up-to-date one has to read /sys/kernel/mm/page_idle/bitmap first.
[IO related page flags]
1. ERROR IO error occurred
3. UPTODATE page has up-to-date data

3
fs/proc/page.c
View File

@ -150,6 +150,9 @@ u64 stable_page_flags(struct page *page)
if (PageBalloon(page))
u |= 1 << KPF_BALLOON;
if (page_is_idle(page))
u |= 1 << KPF_IDLE;
u |= kpf_copy_bit(k, KPF_LOCKED, PG_locked);
u |= kpf_copy_bit(k, KPF_SLAB, PG_slab);

1
include/uapi/linux/kernel-page-flags.h
View File

@ -33,6 +33,7 @@
#define KPF_THP 22
#define KPF_BALLOON 23
#define KPF_ZERO_PAGE 24
#define KPF_IDLE 25
#endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */