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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id 70sm1352466ljj.81.2021.07.07.07.47.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Jul 2021 07:47:53 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 7 Jul 2021 16:47:51 +0200 To: Andrew Morton , Michal Hocko Cc: Andrew Morton , "Uladzislau Rezki (Sony)" , linux-mm@kvack.org, LKML , Mel Gorman , Christoph Hellwig , Matthew Wilcox , Nicholas Piggin , Hillf Danton , Oleksiy Avramchenko , Steven Rostedt Subject: Re: [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Message-ID: <20210707144751.GB1863@pc638.lan> References: <20210705170537.43060-1-urezki@gmail.com> <20210706132653.8374852963b25989e360d599@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 07, 2021 at 10:42:29AM +0200, Michal Hocko wrote: > On Tue 06-07-21 13:26:53, Andrew Morton wrote: > > On Mon, 5 Jul 2021 19:05:36 +0200 "Uladzislau Rezki (Sony)" wrote: > > > > > In case of simultaneous vmalloc allocations, for example it is 1GB and > > > 12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT > > > kernel. > > > > > > > > > ... > > > > > > are obtained, i.e. do batched page requests adding cond_resched() meanwhile > > > to reschedule. Batched value is hard-coded and is 100 pages per call. > > > > > > Signed-off-by: Uladzislau Rezki (Sony) > > > > Can we please have a Fixes: for this? > > Is this a fix for any actual real life problem? I mean allocating 1GB of > vmalloc space back and forth sounds like a stretch to me. > It is not a real scenario. I simulated it by the stress-suite tests. So the Fixes tag is not needed, IMHO. > > Is this fix important enough for 4.14-rcx? I think so... > > I do not think so. This is an improvement so that vmalloc behaves more > sanely for those abusers... > A bulk-allocator has recently been introduced, so 4.x does not have it, i.e. this change is not applicable and 4.x kernel does not suffer from it. -- Vlad Rezki