From: Vladimir Davydov <vdavydov@parallels.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Greg Thelen <gthelen@google.com>,
linux-mm@kvack.org, Michal Hocko <mhocko@suse.cz>,
Dave Hansen <dave@sr71.net>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [patch] mm: memcontrol: support transparent huge pages under pressure
Date: Tue, 23 Sep 2014 15:56:55 +0400 [thread overview]
Message-ID: <20140923115655.GJ18526@esperanza> (raw)
In-Reply-To: <20140923114827.GB13593@cmpxchg.org>
On Tue, Sep 23, 2014 at 07:48:27AM -0400, Johannes Weiner wrote:
> On Tue, Sep 23, 2014 at 12:29:27PM +0400, Vladimir Davydov wrote:
> > On Mon, Sep 22, 2014 at 10:52:50PM -0700, Greg Thelen wrote:
> > > In this condition, if res usage is at limit then there's no point in
> > > swapping because memsw.usage is already maximal. Prior to this patch
> > > I think the kernel did the right thing, but not afterwards.
> > >
> > > Before this patch:
> > > if res.usage == res.limit, try_charge() indirectly calls
> > > try_to_free_mem_cgroup_pages(noswap=true)
> >
> > But this is wrong. If we fail to charge res, we should try to do swap
> > out along with page cache reclaim. Swap out won't affect memsw.usage,
> > but will diminish res.usage so that the allocation may succeed.
>
> But we know that the memsw limit must be hit as well in that case, and
> swapping only makes progress in the sense that we are then succeeding
> the memory charge. But we still fail to charge memsw.
Yeah, I admit I said nonsense. The problem Greg pointed out does exist.
I think your second patch (charging memsw before res) should fix it.
Thanks,
Vladimir
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next prev parent reply other threads:[~2014-09-23 11:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-19 13:20 [patch] mm: memcontrol: support transparent huge pages under pressure Johannes Weiner
2014-09-22 10:18 ` Vladimir Davydov
2014-09-23 5:52 ` Greg Thelen
2014-09-23 8:29 ` Vladimir Davydov
2014-09-23 11:44 ` Vladimir Davydov
2014-09-23 11:48 ` Johannes Weiner
2014-09-23 11:56 ` Vladimir Davydov [this message]
2014-09-23 11:16 ` Johannes Weiner
2014-09-24 0:07 ` Greg Thelen
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