linux-kernel - Re: [PATCH v4 7/8] Display current tcp memory allocation in kmem cgroup

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Message-ID: <20111003123620.GA30018@shutemov.name>
Date:	Mon, 3 Oct 2011 15:36:20 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, paul@...lmenage.org,
	lizf@...fujitsu.com, kamezawa.hiroyu@...fujitsu.com,
	ebiederm@...ssion.com, davem@...emloft.net, gthelen@...gle.com,
	netdev@...r.kernel.org, linux-mm@...ck.org, avagin@...allels.com
Subject: Re: [PATCH v4 7/8] Display current tcp memory allocation in kmem
 cgroup

On Mon, Oct 03, 2011 at 04:26:41PM +0400, Glauber Costa wrote:
> On 10/03/2011 04:25 PM, Kirill A. Shutemov wrote:
> > On Mon, Oct 03, 2011 at 04:19:18PM +0400, Glauber Costa wrote:
> >> On 10/03/2011 04:14 PM, Kirill A. Shutemov wrote:
> >>> On Mon, Oct 03, 2011 at 02:18:42PM +0400, Glauber Costa wrote:
> >>>> This patch introduces kmem.tcp_current_memory file, living in the
> >>>> kmem_cgroup filesystem. It is a simple read-only file that displays the
> >>>> amount of kernel memory currently consumed by the cgroup.
> >>>>
> >>>> Signed-off-by: Glauber Costa<glommer@...allels.com>
> >>>> CC: David S. Miller<davem@...emloft.net>
> >>>> CC: Hiroyouki Kamezawa<kamezawa.hiroyu@...fujitsu.com>
> >>>> CC: Eric W. Biederman<ebiederm@...ssion.com>
> >>>> ---
> >>>>    Documentation/cgroups/memory.txt |    1 +
> >>>>    mm/memcontrol.c                  |   11 +++++++++++
> >>>>    2 files changed, 12 insertions(+), 0 deletions(-)
> >>>>
> >>>> diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
> >>>> index 1ffde3e..f5a539d 100644
> >>>> --- a/Documentation/cgroups/memory.txt
> >>>> +++ b/Documentation/cgroups/memory.txt
> >>>> @@ -79,6 +79,7 @@ Brief summary of control files.
> >>>>     memory.independent_kmem_limit	 # select whether or not kernel memory limits are
> >>>>    				   independent of user limits
> >>>>     memory.kmem.tcp.max_memory      # set/show hard limit for tcp buf memory
> >>>> + memory.kmem.tcp.current_memory  # show current tcp buf memory allocation
> >>>
> >>> Both are in pages, right?
> >>> Shouldn't it be scaled to bytes and named uniform with other memcg file?
> >>> memory.kmem.tcp.limit_in_bytes/usage_in_bytes.
> >>>
> >> You are absolutely correct.
> >> Since the internal tcp comparison works, I just ended up never noticing
> >> this.
> >
> > Should we have failcnt and max_usage_in_bytes for tcp as well?
> >
> 
> Well, we get a fail count from the tracer anyway, so I don't really see 
> a need for that. I see value in having it for the slab allocation 
> itself, but since this only controls the memory pressure framework, I 
> think we can live without it.
> 
> That said, this is not a strong opinion. I can add it if you'd prefer.

It's good for userspace to have the same set of files for all domains:
 - memory;
 - memory.memsw;
 - memory.kmem;
 - memory.kmem.tcp;
 - etc.
Userspace can reuse code for handling them in this case.

-- 
 Kirill A. Shutemov
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