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From: Dave Hansen <dave.hansen@linux.intel.com>
To: linux-kernel@vger.kernel.org
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
	mhocko@suse.com, jannh@google.com, vbabka@suse.cz,
	minchan@kernel.org, dancol@google.com, joel@joelfernandes.org,
	akpm@linux-foundation.org
Subject: [PATCH 0/2] mm/madvise: teach MADV_PAGEOUT about swap cache
Date: Mon, 23 Mar 2020 16:41:47 -0700
Message-ID: <20200323234147.558EBA81@viggo.jf.intel.com> (raw)

MADV_PAGEOUT ignores swap cache pages which are not mapped
into the calling process.  That's nasty because it means that
some of the most easily reclaimable pages are inaccessible to
a mechanism designed to reclaim pages.

This all turned out to be a bit nastier and more complicated
than I would have liked.  This has been lightly tested, but I
did pass a normal barrage of compile tests.

I rigged up a little test program to try to create these
situations.  Basically, if the parent "reader" RSS changes
in response to MADV_PAGEOUT actions in the child, there is
a problem.

	https://www.sr71.net/~dave/intel/madv-pageout.c

I'd add this to selftests, but it *requires* swap to work
and its parsing of /proc/self/maps is quite icky.

P.S. mincore() really doesn't work at all in this situation,
probably something we need to look at too.

Cc: Michal Hocko <mhocko@suse.com>
Cc: Jann Horn <jannh@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Daniel Colascione <dancol@google.com>
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: Andrew Morton <akpm@linux-foundation.org>

             reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-23 23:41 Dave Hansen [this message]
2020-03-23 23:41 ` [PATCH 1/2] mm/madvise: help MADV_PAGEOUT to find swap cache pages Dave Hansen
2020-03-26  6:24   ` Minchan Kim
2020-03-23 23:41 ` [PATCH 2/2] mm/madvise: skip MADV_PAGEOUT on shared " Dave Hansen
2020-03-26  6:28   ` Minchan Kim
2020-03-26 23:00     ` Dave Hansen
2020-03-27  6:42       ` Minchan Kim

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