From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f199.google.com (mail-ig0-f199.google.com [209.85.213.199]) by kanga.kvack.org (Postfix) with ESMTP id B44796B0253 for ; Tue, 24 May 2016 12:36:15 -0400 (EDT) Received: by mail-ig0-f199.google.com with SMTP id u5so41274177igk.2 for ; Tue, 24 May 2016 09:36:15 -0700 (PDT) Received: from emea01-am1-obe.outbound.protection.outlook.com (mail-am1on0105.outbound.protection.outlook.com. [157.56.112.105]) by mx.google.com with ESMTPS id x7si2587138oia.49.2016.05.24.09.36.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 24 May 2016 09:36:14 -0700 (PDT) Date: Tue, 24 May 2016 19:36:06 +0300 From: Vladimir Davydov Subject: Re: [PATCH RESEND 8/8] af_unix: charge buffers to kmemcg Message-ID: <20160524163606.GB11150@esperanza> References: <1464094926.5939.48.camel@edumazet-glaptop3.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1464094926.5939.48.camel@edumazet-glaptop3.roam.corp.google.com> Sender: owner-linux-mm@kvack.org List-ID: To: Eric Dumazet Cc: Andrew Morton , "David S. Miller" , Johannes Weiner , Michal Hocko , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org On Tue, May 24, 2016 at 06:02:06AM -0700, Eric Dumazet wrote: > 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 lands in a > different socket , maybe owned by another user/process. > > Who owns it now, in term of kmemcg accounting ? We never move memcg charges. E.g. if two processes from different cgroups are sharing a memory region, each page will be charged to the process which touched it first. Or if two processes are working with the same directory tree, inodes and dentries will be charged to the first user. The same is fair for unix socket buffers - they will be charged to the sender. > > 2) Has performance impact been evaluated ? I ran netperf STREAM_STREAM with default options in a kmemcg on a 4 core x 2 HT box. The results are below: # clients bandwidth (10^6bits/sec) base patched 1 67643 +- 725 64874 +- 353 - 4.0 % 4 193585 +- 2516 186715 +- 1460 - 3.5 % 8 194820 +- 377 187443 +- 1229 - 3.7 % So the accounting doesn't come for free - it takes ~4% of performance. I believe we could optimize it by using per cpu batching not only on charge, but also on uncharge in memcg core, but that's beyond the scope of this patch set - I'll take a look at this later. Anyway, if performance impact is found to be unacceptable, it is always possible to disable kmem accounting at boot time (cgroup.memory=nokmem) or not use memory cgroups at runtime at all (thanks to jump labels there'll be no overhead even if they are compiled in). Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org