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Message-ID: <ukrl43rakgdzlo4fvw3ldwyoke76dgnseobtf75ldghe3fadxc@ag2y4jk77js2>
Date: Fri, 30 Aug 2024 12:44:34 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>,
Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>,
David Rientjes <rientjes@...gle.com>, Hyeonggon Yoo <42.hyeyoo@...il.com>,
Eric Dumazet <edumazet@...gle.com>, "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Meta kernel team <kernel-team@...a.com>, cgroups@...r.kernel.org,
netdev@...r.kernel.org
Subject: Re: [PATCH v3] memcg: add charging of already allocated slab objects
On Fri, Aug 30, 2024 at 11:07:32AM GMT, Vlastimil Babka wrote:
> On 8/29/24 19:53, Shakeel Butt wrote:
> > At the moment, the slab objects are charged to the memcg at the
> > allocation time. However there are cases where slab objects are
> > allocated at the time where the right target memcg to charge it to is
> > not known. One such case is the network sockets for the incoming
> > connection which are allocated in the softirq context.
> >
> > Couple hundred thousand connections are very normal on large loaded
> > server and almost all of those sockets underlying those connections get
> > allocated in the softirq context and thus not charged to any memcg.
> > However later at the accept() time we know the right target memcg to
> > charge. Let's add new API to charge already allocated objects, so we can
> > have better accounting of the memory usage.
> >
> > To measure the performance impact of this change, tcp_crr is used from
> > the neper [1] performance suite. Basically it is a network ping pong
> > test with new connection for each ping pong.
> >
> > The server and the client are run inside 3 level of cgroup hierarchy
> > using the following commands:
> >
> > Server:
> > $ tcp_crr -6
> >
> > Client:
> > $ tcp_crr -6 -c -H ${server_ip}
> >
> > If the client and server run on different machines with 50 GBPS NIC,
> > there is no visible impact of the change.
> >
> > For the same machine experiment with v6.11-rc5 as base.
> >
> > base (throughput) with-patch
> > tcp_crr 14545 (+- 80) 14463 (+- 56)
> >
> > It seems like the performance impact is within the noise.
> >
> > Link: https://github.com/google/neper [1]
> > Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
>
> Thanks, pushed to slab/for-next for test coverage, hopefully net people will
> ack.
>
> Also one thing:
>
> We should add some kernel doc for this, no? Explaining when people are
> supposed to use this, that objects from KMALLOC_NORMAL will be ignored, and
> what the return value means (including where it's faked to be true).
>
Yes this makes sense. I will add this info similar to the kmalloc()
have. Should I send a v4 with this details?
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