Date: Sun, 4 Jun 2017 12:38:50 -0700
From: Yu Zhao <yuzhao@google.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>, cgroups@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] swap: cond_resched in swap_cgroup_prepare()
Message-ID: <20170604193850.GA15369@google.com>
References: <20170601195635.20744-1-yuzhao@google.com>
 <20170602081855.GE29840@dhcp22.suse.cz>
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On Fri, Jun 02, 2017 at 10:18:57AM +0200, Michal Hocko wrote:
> On Thu 01-06-17 12:56:35, Yu Zhao wrote:
> > Saw need_resched() warnings when swapping on large swapfile (TBs)
> > because page allocation in swap_cgroup_prepare() took too long.
> 
> Hmm, but the page allocator makes sure to cond_resched for sleeping
> allocations. I guess what you mean is something different. It is not the
> allocation which took too look but there are too many of them and none
> of them sleeps because there is enough memory and the allocator doesn't
> sleep in that case. Right?
> 
> > We already cond_resched when freeing page in swap_cgroup_swapoff().
> > Do the same for the page allocation.
> > 
> > Signed-off-by: Yu Zhao <yuzhao@google.com>
> 
> The patch itself makes sense to me, the changelog could see some
> clarification but other than that
> Acked-by: Michal Hocko <mhocko@suse.com>

Thanks, I'll clarify the problem in the commit message and resend the
patch.