netdev - Re: [PATCH v2] memcg: add charging of already allocated slab objects

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Message-ID: <ZtIs5qx0QBB8FqGI@google.com>
Date: Fri, 30 Aug 2024 20:34:46 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Muchun Song <muchun.song@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	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 v2] memcg: add charging of already allocated slab objects

On Tue, Aug 27, 2024 at 04:52:28PM -0700, Shakeel Butt wrote:
41;2500;0c> 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>

Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>

Thanks!