From: Vladimir Davydov <vdavydov@virtuozzo.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: "David S. Miller" <davem@davemloft.net>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>, Tejun Heo <tj@kernel.org>,
netdev@vger.kernel.org, linux-mm@kvack.org,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/8] mm: memcontrol: account socket memory in unified hierarchy
Date: Thu, 22 Oct 2015 21:45:10 +0300 [thread overview]
Message-ID: <20151022184509.GM18351@esperanza> (raw)
In-Reply-To: <1445487696-21545-1-git-send-email-hannes@cmpxchg.org>
Hi Johannes,
On Thu, Oct 22, 2015 at 12:21:28AM -0400, Johannes Weiner wrote:
...
> Patch #5 adds accounting and tracking of socket memory to the unified
> hierarchy memory controller, as described above. It uses the existing
> per-cpu charge caches and triggers high limit reclaim asynchroneously.
>
> Patch #8 uses the vmpressure extension to equalize pressure between
> the pages tracked natively by the VM and socket buffer pages. As the
> pool is shared, it makes sense that while natively tracked pages are
> under duress the network transmit windows are also not increased.
First of all, I've no experience in networking, so I'm likely to be
mistaken. Nevertheless I beg to disagree that this patch set is a step
in the right direction. Here goes why.
I admit that your idea to get rid of explicit tcp window control knobs
and size it dynamically basing on memory pressure instead does sound
tempting, but I don't think it'd always work. The problem is that in
contrast to, say, dcache, we can't shrink tcp buffers AFAIU, we can only
stop growing them. Now suppose a system hasn't experienced memory
pressure for a while. If we don't have explicit tcp window limit, tcp
buffers on such a system might have eaten almost all available memory
(because of network load/problems). If a user workload that needs a
significant amount of memory is started suddenly then, the network code
will receive a notification and surely stop growing buffers, but all
those buffers accumulated won't disappear instantly. As a result, the
workload might be unable to find enough free memory and have no choice
but invoke OOM killer. This looks unexpected from the user POV.
That said, I think we do need per memcg tcp window control similar to
what we have system-wide. In other words, Glauber's work makes sense to
me. You might want to point me at my RFC patch where I proposed to
revert it (https://lkml.org/lkml/2014/9/12/401). Well, I've changed my
mind since then. Now I think I was mistaken, luckily I was stopped.
However, I may be mistaken again :-)
Thanks,
Vladimir
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next prev parent reply other threads:[~2015-10-22 18:45 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-22 4:21 [PATCH 0/8] mm: memcontrol: account socket memory in unified hierarchy Johannes Weiner
2015-10-22 4:21 ` [PATCH 1/8] mm: page_counter: let page_counter_try_charge() return bool Johannes Weiner
2015-10-23 11:31 ` Michal Hocko
2015-10-22 4:21 ` [PATCH 2/8] mm: memcontrol: export root_mem_cgroup Johannes Weiner
2015-10-23 11:32 ` Michal Hocko
2015-10-22 4:21 ` [PATCH 3/8] net: consolidate memcg socket buffer tracking and accounting Johannes Weiner
2015-10-22 18:46 ` Vladimir Davydov
2015-10-22 19:09 ` Johannes Weiner
2015-10-23 13:42 ` Vladimir Davydov
2015-10-23 12:38 ` Michal Hocko
2015-10-22 4:21 ` [PATCH 4/8] mm: memcontrol: prepare for unified hierarchy socket accounting Johannes Weiner
2015-10-23 12:39 ` Michal Hocko
2015-10-22 4:21 ` [PATCH 5/8] mm: memcontrol: account socket memory on unified hierarchy Johannes Weiner
2015-10-22 18:47 ` Vladimir Davydov
2015-10-23 13:19 ` Michal Hocko
2015-10-23 13:59 ` David Miller
2015-10-26 16:56 ` Johannes Weiner
2015-10-27 12:26 ` Michal Hocko
2015-10-27 13:49 ` David Miller
2015-10-27 15:41 ` Johannes Weiner
2015-10-27 16:15 ` Michal Hocko
2015-10-27 16:42 ` Johannes Weiner
2015-10-28 0:45 ` David Miller
2015-10-28 3:05 ` Johannes Weiner
2015-10-29 15:25 ` Michal Hocko
2015-10-29 16:10 ` Johannes Weiner
2015-11-04 10:42 ` Michal Hocko
2015-11-04 19:50 ` Johannes Weiner
2015-11-05 14:40 ` Michal Hocko
2015-11-05 16:16 ` David Miller
2015-11-05 16:28 ` Michal Hocko
2015-11-05 16:30 ` David Miller
2015-11-05 22:32 ` Johannes Weiner
2015-11-06 12:51 ` Michal Hocko
2015-11-05 20:55 ` Johannes Weiner
2015-11-05 22:52 ` Johannes Weiner
2015-11-06 10:57 ` Michal Hocko
2015-11-06 16:19 ` Johannes Weiner
2015-11-06 16:46 ` Michal Hocko
2015-11-06 17:45 ` Johannes Weiner
2015-11-07 3:45 ` David Miller
2015-11-12 18:36 ` Mel Gorman
2015-11-12 19:12 ` Johannes Weiner
2015-11-06 9:05 ` Vladimir Davydov
2015-11-06 13:29 ` Michal Hocko
2015-11-06 16:35 ` Johannes Weiner
2015-11-06 13:21 ` Michal Hocko
2015-10-22 4:21 ` [PATCH 6/8] mm: vmscan: simplify memcg vs. global shrinker invocation Johannes Weiner
2015-10-23 13:26 ` Michal Hocko
2015-10-22 4:21 ` [PATCH 7/8] mm: vmscan: report vmpressure at the level of reclaim activity Johannes Weiner
2015-10-22 18:48 ` Vladimir Davydov
2015-10-23 13:49 ` Michal Hocko
2015-10-22 4:21 ` [PATCH 8/8] mm: memcontrol: hook up vmpressure to socket pressure Johannes Weiner
2015-10-22 18:57 ` Vladimir Davydov
2015-10-22 18:45 ` Vladimir Davydov [this message]
2015-10-26 17:22 ` [PATCH 0/8] mm: memcontrol: account socket memory in unified hierarchy Johannes Weiner
2015-10-27 8:43 ` Vladimir Davydov
2015-10-27 16:01 ` Johannes Weiner
2015-10-28 8:20 ` Vladimir Davydov
2015-10-28 18:58 ` Johannes Weiner
2015-10-29 9:27 ` Vladimir Davydov
2015-10-29 17:52 ` Johannes Weiner
2015-11-02 14:47 ` Vladimir Davydov
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