linux-kernel - Re: [PATCH] memcg: drain all stocks for the cgroup before read usage

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20110908091914.6daeab1e.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 8 Sep 2011 09:19:14 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Balbir Singh <bsingharora@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg: drain all stocks for the cgroup before read
 usage

On Thu, 8 Sep 2011 00:33:40 +0300
"Kirill A. Shutemov" <kirill@...temov.name> wrote:

> On Mon, Sep 05, 2011 at 10:16:07AM +0900, Daisuke Nishimura wrote:
> > On Mon, 5 Sep 2011 08:59:13 +0900
> > KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> > 
> > > On Sun,  4 Sep 2011 04:15:33 +0300
> > > "Kirill A. Shutemov" <kirill@...temov.name> wrote:
> > > 
> > > > From: "Kirill A. Shutemov" <kirill@...temov.name>
> > > > 
> > > > Currently, mem_cgroup_usage() for non-root cgroup returns usage
> > > > including stocks.
> > > > 
> > > > Let's drain all socks before read resource counter value. It makes
> > > > memory{,.memcg}.usage_in_bytes and memory.stat consistent.
> > > > 
> > > > Signed-off-by: Kirill A. Shutemov <kirill@...temov.name>
> > > 
> > > Hmm. This seems costly to me. 
> > > 
> > > If a user chesk usage_in_bytes in a memcg once per 1sec, 
> > > the kernel will call schedule_work on cpus once per 1sec.
> > > So, IMHO, I don't like this.
> > > 
> > I agree.
> > 
> > We discussed a similar topic on the thread https://lkml.org/lkml/2011/3/18/212.
> > And, we added the memory.txt:
> > ---
> > 5.5 usage_in_bytes
> > 
> > For efficiency, as other kernel components, memory cgroup uses some optimization
> > to avoid unnecessary cacheline false sharing. usage_in_bytes is affected by the
> > method and doesn't show 'exact' value of memory(and swap) usage, it's an fuzz
> > value for efficient access. (Of course, when necessary, it's synchronized.)
> > If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP)
> > value in memory.stat(see 5.2).
> > ---
> 
> Agree, thanks.
> 
> Should we have field 'ram' (or 'memory') for rss+cache in memory.stat?
> 

Why do you think so ?

Thanks,
-Kame


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/