From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Tim Murray <timmurray@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
Suren Baghdasaryan <surenb@google.com>,
Daniel Colascione <dancol@google.com>,
Shakeel Butt <shakeelb@google.com>,
Sonny Rao <sonnyrao@google.com>,
Brian Geffon <bgeffon@google.com>,
linux-api@vger.kernel.org
Subject: Re: [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER
Date: Mon, 27 May 2019 14:44:11 +0200 [thread overview]
Message-ID: <20190527124411.GC1658@dhcp22.suse.cz> (raw)
In-Reply-To: <20190527075811.GC6879@google.com>
On Mon 27-05-19 16:58:11, Minchan Kim wrote:
> On Tue, May 21, 2019 at 08:26:28AM +0200, Michal Hocko wrote:
> > On Tue 21-05-19 11:55:33, Minchan Kim wrote:
> > > On Mon, May 20, 2019 at 11:28:01AM +0200, Michal Hocko wrote:
> > > > [cc linux-api]
> > > >
> > > > On Mon 20-05-19 12:52:54, Minchan Kim wrote:
> > > > > System could have much faster swap device like zRAM. In that case, swapping
> > > > > is extremely cheaper than file-IO on the low-end storage.
> > > > > In this configuration, userspace could handle different strategy for each
> > > > > kinds of vma. IOW, they want to reclaim anonymous pages by MADV_COLD
> > > > > while it keeps file-backed pages in inactive LRU by MADV_COOL because
> > > > > file IO is more expensive in this case so want to keep them in memory
> > > > > until memory pressure happens.
> > > > >
> > > > > To support such strategy easier, this patch introduces
> > > > > MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER options in madvise(2) like
> > > > > that /proc/<pid>/clear_refs already has supported same filters.
> > > > > They are filters could be Ored with other existing hints using top two bits
> > > > > of (int behavior).
> > > >
> > > > madvise operates on top of ranges and it is quite trivial to do the
> > > > filtering from the userspace so why do we need any additional filtering?
> > > >
> > > > > Once either of them is set, the hint could affect only the interested vma
> > > > > either anonymous or file-backed.
> > > > >
> > > > > With that, user could call a process_madvise syscall simply with a entire
> > > > > range(0x0 - 0xFFFFFFFFFFFFFFFF) but either of MADV_ANONYMOUS_FILTER and
> > > > > MADV_FILE_FILTER so there is no need to call the syscall range by range.
> > > >
> > > > OK, so here is the reason you want that. The immediate question is why
> > > > cannot the monitor do the filtering from the userspace. Slightly more
> > > > work, all right, but less of an API to expose and that itself is a
> > > > strong argument against.
> > >
> > > What I should do if we don't have such filter option is to enumerate all of
> > > vma via /proc/<pid>/maps and then parse every ranges and inode from string,
> > > which would be painful for 2000+ vmas.
> >
> > Painful is not an argument to add a new user API. If the existing API
> > suits the purpose then it should be used. If it is not usable, we can
> > think of a different way.
>
> I measured 1568 vma parsing overhead of /proc/<pid>/maps in ARM64 modern
> mobile CPU. It takes 60ms and 185ms on big cores depending on cpu governor.
> It's never trivial.
This is not the only option. Have you tried to simply use
/proc/<pid>/map_files interface? This will provide you with all the file
backed mappings.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-05-27 12:44 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190520035254.57579-1-minchan@kernel.org>
[not found] ` <20190520035254.57579-2-minchan@kernel.org>
2019-05-20 8:16 ` [RFC 1/7] mm: introduce MADV_COOL Michal Hocko
2019-05-20 8:19 ` Michal Hocko
2019-05-20 15:08 ` Suren Baghdasaryan
2019-05-20 22:55 ` Minchan Kim
2019-05-20 22:54 ` Minchan Kim
2019-05-21 6:04 ` Michal Hocko
2019-05-21 9:11 ` Minchan Kim
2019-05-21 10:05 ` Michal Hocko
[not found] ` <20190520035254.57579-4-minchan@kernel.org>
2019-05-20 8:27 ` [RFC 3/7] mm: introduce MADV_COLD Michal Hocko
2019-05-20 23:00 ` Minchan Kim
2019-05-21 6:08 ` Michal Hocko
2019-05-21 9:13 ` Minchan Kim
[not found] ` <20190520035254.57579-6-minchan@kernel.org>
2019-05-20 9:18 ` [RFC 5/7] mm: introduce external memory hinting API Michal Hocko
2019-05-21 2:41 ` Minchan Kim
2019-05-21 6:17 ` Michal Hocko
2019-05-21 10:32 ` Minchan Kim
[not found] ` <20190520035254.57579-7-minchan@kernel.org>
2019-05-20 9:22 ` [RFC 6/7] mm: extend process_madvise syscall to support vector arrary Michal Hocko
2019-05-21 2:48 ` Minchan Kim
2019-05-21 6:24 ` Michal Hocko
2019-05-21 10:26 ` Minchan Kim
2019-05-21 10:37 ` Michal Hocko
2019-05-27 7:49 ` Minchan Kim
2019-05-29 10:08 ` Daniel Colascione
2019-05-29 10:33 ` Michal Hocko
2019-05-30 2:17 ` Minchan Kim
2019-05-30 6:57 ` Michal Hocko
2019-05-30 8:02 ` Minchan Kim
2019-05-30 16:19 ` Daniel Colascione
2019-05-30 18:47 ` Michal Hocko
[not found] ` <20190520035254.57579-8-minchan@kernel.org>
2019-05-20 9:28 ` [RFC 7/7] mm: madvise support MADV_ANONYMOUS_FILTER and MADV_FILE_FILTER Michal Hocko
2019-05-21 2:55 ` Minchan Kim
2019-05-21 6:26 ` Michal Hocko
2019-05-27 7:58 ` Minchan Kim
2019-05-27 12:44 ` Michal Hocko [this message]
2019-05-28 3:26 ` Minchan Kim
2019-05-28 6:29 ` Michal Hocko
2019-05-28 8:13 ` Minchan Kim
2019-05-28 8:31 ` Daniel Colascione
2019-05-28 8:49 ` Minchan Kim
2019-05-28 9:08 ` Michal Hocko
2019-05-28 9:39 ` Daniel Colascione
2019-05-28 10:33 ` Michal Hocko
2019-05-28 11:21 ` Daniel Colascione
2019-05-28 11:49 ` Michal Hocko
2019-05-28 12:11 ` Daniel Colascione
2019-05-28 12:32 ` Michal Hocko
2019-05-28 10:32 ` Minchan Kim
2019-05-28 10:41 ` Michal Hocko
2019-05-28 11:12 ` Minchan Kim
2019-05-28 11:28 ` Michal Hocko
2019-05-28 11:42 ` Daniel Colascione
2019-05-28 11:56 ` Michal Hocko
2019-05-28 12:18 ` Daniel Colascione
2019-05-28 12:38 ` Michal Hocko
2019-05-28 12:10 ` Minchan Kim
2019-05-28 11:44 ` Minchan Kim
2019-05-28 11:51 ` Daniel Colascione
2019-05-28 12:06 ` Michal Hocko
2019-05-28 12:22 ` Minchan Kim
2019-05-28 11:28 ` Daniel Colascione
2019-05-21 15:33 ` Johannes Weiner
2019-05-22 1:50 ` Minchan Kim
2019-05-20 9:28 ` [RFC 0/7] introduce memory hinting API for external process Michal Hocko
[not found] ` <20190520164605.GA11665@cmpxchg.org>
[not found] ` <20190521043950.GJ10039@google.com>
2019-05-21 6:32 ` Michal Hocko
[not found] ` <20190521014452.GA6738@bombadil.infradead.org>
2019-05-21 6:34 ` Michal Hocko
2019-05-21 12:53 ` Shakeel Butt
[not found] ` <dbe801f0-4bbe-5f6e-9053-4b7deb38e235@arm.com>
[not found] ` <CAEe=Sxka3Q3vX+7aWUJGKicM+a9Px0rrusyL+5bB1w4ywF6N4Q@mail.gmail.com>
[not found] ` <1754d0ef-6756-d88b-f728-17b1fe5d5b07@arm.com>
2019-05-21 12:56 ` Shakeel Butt
2019-05-22 4:23 ` Brian Geffon
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