From: Michal Hocko <mhocko@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Miller <davem@davemloft.net>,
akpm@linux-foundation.org, vdavydov@virtuozzo.com, tj@kernel.org,
netdev@vger.kernel.org, linux-mm@kvack.org,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/8] mm: memcontrol: account socket memory on unified hierarchy
Date: Thu, 29 Oct 2015 16:25:46 +0100 [thread overview]
Message-ID: <20151029152546.GG23598@dhcp22.suse.cz> (raw)
In-Reply-To: <20151027164227.GB7749@cmpxchg.org>
On Tue 27-10-15 09:42:27, Johannes Weiner wrote:
> On Tue, Oct 27, 2015 at 05:15:54PM +0100, Michal Hocko wrote:
> > On Tue 27-10-15 11:41:38, Johannes Weiner wrote:
[...]
> Or it could be exactly the other way around when you have a workload
> that is heavy on filesystem metadata. I don't see why any scenario
> would be more important than the other.
Yes I definitely agree. No scenario is more important. We can only
come up with a default that makes more sense for the majority and
allow the minority to override. That was what I wanted to say basically.
> I'm not saying that distinguishing between consumers is wrong, just
> that "user memory vs kernel memory" is a false classification. Why do
> you call page cache user memory but dentry cache kernel memory? It
> doesn't make any sense.
We are not talking about dcache vs. page cache alone here, though. We
are talking about _all_ slab allocations vs. only user accessed memory.
The slab consumption is directly under kernel control. A great pile of
this logic is completly hidden from userspace. While user can estimate
the user memory it is hard (if possible) to do that for the kernel
memory footprint - not even mentioning this is variable and dependent on
the particular kernel version.
> > Also kmem accounting will make the load more non-deterministic because
> > many of the resources are shared between tasks in separate cgroups
> > unless they are explicitly configured. E.g. [id]cache will be shared
> > and first to touch gets charged so you would end up with more false
> > sharing.
>
> Exactly like page cache. This differentiation isn't based on reality.
Yes false sharing is an existing and long term problem already. I just
wanted to point out that the false sharing would be even a bigger
problem because some kernel tracked resources are shared more naturally
than file sharing.
> > > IMO that's an implementation detail and a historical artifact that
> > > should not be exposed to the user. And that's the thing I hate about
> > > the current opt-out knob.
>
> You carefully skipped over this part. We can ignore it for socket
> memory but it's something we need to figure out when it comes to slab
> accounting and tracking.
I am sorry, I didn't mean to skip this part, I though it would be clear
from the previous text. I think kmem accounting falls into the same
category. Have a sane default and a global boottime knob to override it
for those that think differently - for whatever reason they might have.
[...]
> Having page cache accounting built in while presenting dentry+inode
> cache as a configurable extension is completely random and doesn't
> make sense. They are both first class memory consumers. They're not
> separate categories. One isn't more "core" than the other.
Again we are talking about all slab allocations not just the dcache.
> > > For now, something like this as a boot commandline?
> > >
> > > cgroup.memory=nosocket
> >
> > That would work for me.
>
> Okay, then I'll go that route for the socket stuff.
Thanks!
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2015-10-29 15:25 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 [this message]
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 ` [PATCH 0/8] mm: memcontrol: account socket memory in unified hierarchy Vladimir Davydov
2015-10-26 17:22 ` 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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