Re: [PATCH -mm v9 7/8] proc: export idle flag via kpageflags

Andrew Morton
2015-07-21T23:35:00Z

On Sun, 19 Jul 2015 15:31:16 +0300 Vladimir Davydov <vdavydov@parallels.com> 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.

Is there any value in teaching the regular old page scanner to update
these flags? If it's doing an rmap scan anyway...

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