On Wed, Jul 15, 2015 at 6:54 AM, Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> wrote: > 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 > /proc/kpageidle first. > > Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Reviewed-by: Andres Lagar-Cavilla <andreslc@xxxxxxxxxx> > --- > Documentation/vm/pagemap.txt | 6 ++++++ > fs/proc/page.c | 3 +++ > include/uapi/linux/kernel-page-flags.h | 1 + > 3 files changed, 10 insertions(+) > > diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt > index c9266340852c..5896b7d7fd74 100644 > --- a/Documentation/vm/pagemap.txt > +++ b/Documentation/vm/pagemap.txt > @@ -64,6 +64,7 @@ There are five 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 > @@ -124,6 +125,11 @@ 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 /proc/kpageidle) > + 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 /proc/kpageidle first. > + > [IO related page flags] > 1. ERROR IO error occurred > 3. UPTODATE page has up-to-date data > diff --git a/fs/proc/page.c b/fs/proc/page.c > index 273537885ab4..13dcb823fe4e 100644 > --- a/fs/proc/page.c > +++ b/fs/proc/page.c > @@ -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); > diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h > index a6c4962e5d46..5da5f8751ce7 100644 > --- a/include/uapi/linux/kernel-page-flags.h > +++ b/include/uapi/linux/kernel-page-flags.h > @@ -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 */ > -- > 2.1.4 > -- Andres Lagar-Cavilla | Google Kernel Team | andreslc@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
