linux-kernel - Re: [PATCH RESEND 8/8] af_unix: charge buffers to kmemcg

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Message-ID: <1464094926.5939.48.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Tue, 24 May 2016 06:02:06 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 8/8] af_unix: charge buffers to kmemcg

On Tue, 2016-05-24 at 11:49 +0300, Vladimir Davydov wrote:
> Unix sockets can consume a significant amount of system memory, hence
> they should be accounted to kmemcg.
> 
> Since unix socket buffers are always allocated from process context,
> all we need to do to charge them to kmemcg is set __GFP_ACCOUNT in
> sock->sk_allocation mask.

I have two questions : 

1) What happens when a buffer, allocated from socket <A> lands in a
different socket <B>, maybe owned by another user/process.

Who owns it now, in term of kmemcg accounting ?

2) Has performance impact been evaluated ?

Thanks.