linux-kernel - Re: [PATCH] swap: cond_resched in swap_cgroup

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Message-ID: <20170604193850.GA15369@google.com>
Date:   Sun, 4 Jun 2017 12:38:50 -0700
From:   Yu Zhao <yuzhao@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] swap: cond_resched in swap_cgroup_prepare()

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@...gle.com>
> 
> The patch itself makes sense to me, the changelog could see some
> clarification but other than that
> Acked-by: Michal Hocko <mhocko@...e.com>

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