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Commit f074a8f4 authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
Browse files

proc: export idle flag via kpageflags 



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: default avatarVladimir Davydov <vdavydov@parallels.com>
Reviewed-by: default avatarAndres 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 33c3fc71

Documentation/vm/pagemap.txt

+7 −0
Original line number Diff line number Diff line
@@ -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

fs/proc/page.c

+3 −0
Original line number Diff line number Diff line
@@ -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);

include/uapi/linux/kernel-page-flags.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */