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[108.27.252.85]) by smtp.gmail.com with ESMTPSA id q15sm25893828vka.44.2019.07.29.08.49.52 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 29 Jul 2019 08:49:53 -0700 (PDT) Date: Mon, 29 Jul 2019 11:49:52 -0400 From: Johannes Weiner To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Michal Hocko , Vladimir Davydov Subject: Re: [PATCH RFC] mm/memcontrol: reclaim severe usage over high limit in get_user_pages loop Message-ID: <20190729154952.GC21958@cmpxchg.org> References: <156431697805.3170.6377599347542228221.stgit@buzz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <156431697805.3170.6377599347542228221.stgit@buzz> User-Agent: Mutt/1.12.0 (2019-05-25) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, Jul 28, 2019 at 03:29:38PM +0300, Konstantin Khlebnikov wrote: > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -847,8 +847,11 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > ret = -ERESTARTSYS; > goto out; > } > - cond_resched(); > > + /* Reclaim memory over high limit before stocking too much */ > + mem_cgroup_handle_over_high(true); I'd rather this remained part of the try_charge() call. The code comment in try_charge says this: * We can perform reclaim here if __GFP_RECLAIM but let's * always punt for simplicity and so that GFP_KERNEL can * consistently be used during reclaim. The simplicity argument doesn't hold true anymore once we have to add manual calls into allocation sites. We should instead fix try_charge() to do synchronous reclaim for __GFP_RECLAIM and only punt to userspace return when actually needed.