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From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-api@vger.kernel.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>,
	jannh@google.com, oleg@redhat.com, christian@brauner.io,
	oleksandr@redhat.com, hdanton@sina.com
Subject: Re: [RFCv2 1/6] mm: introduce MADV_COLD
Date: Tue, 4 Jun 2019 09:02:28 +0200
Message-ID: <20190604070228.GD4669@dhcp22.suse.cz> (raw)
In-Reply-To: <20190604042651.GC43390@google.com>

On Tue 04-06-19 13:26:51, Minchan Kim wrote:
> On Mon, Jun 03, 2019 at 09:16:07AM +0200, Michal Hocko wrote:
[...]
> > Right. But there is still the page cache reclaim. Is it expected that
> > an explicitly cold memory doesn't get reclaimed because we have a
> > sufficient amount of page cache (a very common case) and we never age
> > anonymous memory because of that?
> 
> If there are lots of used-once pages in file-LRU, I think there is no
> need to reclaim anonymous pages because it needs bigger overhead due to
> IO. It has been true for a long time in current VM policy.

You are making an assumption which is not universally true. If I _know_
that there is a considerable amount of idle anonymous memory then I
would really prefer if it goes to the swap rather than make a pressure
on caching. Inactive list is not guaranteed to contain only used-once
pages, right?

Anyway, as already mentioned, we can start with a simpler implementation
for now and explicitly note that pagecache biased reclaim is known to be
a problem potentially. I am pretty sure somebody will come sooner or
later and we can address the problem then with some good numbers to back
the additional complexity.

-- 
Michal Hocko
SUSE Labs

  reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-31  6:43 [RFCv2 0/6] introduce memory hinting API for external process Minchan Kim
2019-05-31  6:43 ` [RFCv2 1/6] mm: introduce MADV_COLD Minchan Kim
2019-05-31  8:47   ` Michal Hocko
2019-05-31 13:39     ` Minchan Kim
2019-05-31 14:03       ` Michal Hocko
2019-05-31 14:34         ` Minchan Kim
2019-06-03  7:16           ` Michal Hocko
2019-06-03 15:43             ` Daniel Colascione
2019-06-03 17:27             ` Johannes Weiner
2019-06-03 20:32               ` Michal Hocko
2019-06-03 21:50                 ` Johannes Weiner
2019-06-03 23:02                   ` Minchan Kim
2019-06-04  6:56                     ` Michal Hocko
2019-06-04 12:06                     ` Johannes Weiner
2019-06-04  6:55                   ` Michal Hocko
2019-06-04  4:26             ` Minchan Kim
2019-06-04  7:02               ` Michal Hocko [this message]
2019-05-31  6:43 ` [RFCv2 2/6] mm: change PAGEREF_RECLAIM_CLEAN with PAGE_REFRECLAIM Minchan Kim
2019-05-31  6:43 ` [RFCv2 3/6] mm: introduce MADV_PAGEOUT Minchan Kim
2019-05-31  8:50   ` Michal Hocko
2019-05-31 13:44     ` Minchan Kim
2019-05-31 16:59   ` Johannes Weiner
2019-05-31 23:14     ` Minchan Kim
2019-05-31  6:43 ` [RFCv2 4/6] mm: factor out madvise's core functionality Minchan Kim
2019-05-31  7:04   ` Oleksandr Natalenko
2019-05-31 13:12     ` Minchan Kim
2019-05-31 14:35       ` Oleksandr Natalenko
2019-05-31 23:29         ` Minchan Kim
2019-06-05 13:27           ` Oleksandr Natalenko
2019-06-10 10:12             ` Minchan Kim
2019-05-31  6:43 ` [RFCv2 5/6] mm: introduce external memory hinting API Minchan Kim
2019-05-31  8:37   ` Michal Hocko
2019-05-31 13:19     ` Minchan Kim
2019-05-31 14:00       ` Michal Hocko
2019-05-31 14:11         ` Minchan Kim
2019-05-31 17:35   ` Daniel Colascione
2019-05-31  6:43 ` [RFCv2 6/6] mm: extend process_madvise syscall to support vector arrary Minchan Kim
2019-05-31 10:06   ` Yann Droneaud
2019-05-31 23:18     ` Minchan Kim

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