From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f44.google.com (mail-pa0-f44.google.com [209.85.220.44]) by kanga.kvack.org (Postfix) with ESMTP id CBD296B0005 for ; Thu, 11 Feb 2016 16:18:05 -0500 (EST) Received: by mail-pa0-f44.google.com with SMTP id ho8so34884505pac.2 for ; Thu, 11 Feb 2016 13:18:05 -0800 (PST) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTP id k81si14801138pfj.154.2016.02.11.13.18.04 for ; Thu, 11 Feb 2016 13:18:05 -0800 (PST) Message-ID: <1455225484.715.93.camel@schen9-desk2.jf.intel.com> Subject: Re: [RFC PATCH 3/3] mm: increase scalability of global memory commitment accounting From: Tim Chen Date: Thu, 11 Feb 2016 13:18:04 -0800 In-Reply-To: <20160211125103.8a4fb0ffed593938321755d2@linux-foundation.org> References: <1455115941-8261-1-git-send-email-aryabinin@virtuozzo.com> <1455115941-8261-3-git-send-email-aryabinin@virtuozzo.com> <1455127253.715.36.camel@schen9-desk2.jf.intel.com> <20160210132818.589451dbb5eafae3fdb4a7ec@linux-foundation.org> <1455150256.715.60.camel@schen9-desk2.jf.intel.com> <20160211125103.8a4fb0ffed593938321755d2@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Andrey Ryabinin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andi Kleen , Mel Gorman , Vladimir Davydov , Konstantin Khlebnikov On Thu, 2016-02-11 at 12:51 -0800, Andrew Morton wrote: > On Wed, 10 Feb 2016 16:24:16 -0800 Tim Chen wrote: > > > On Wed, 2016-02-10 at 13:28 -0800, Andrew Morton wrote: > > > > > > > > If a process is unmapping 4MB then it's pretty crazy for us to be > > > hitting the percpu_counter 32 separate times for that single operation. > > > > > > Is there some way in which we can batch up the modifications within the > > > caller and update the counter less frequently? Perhaps even in a > > > single hit? > > > > I think the problem is the batch size is too small and we overflow > > the local counter into the global counter for 4M allocations. > > That's one way of looking at the issue. The other way (which I point > out above) is that we're calling vm_[un]_acct_memory too frequently > when mapping/unmapping 4M segments. > > Exactly which mmap.c callsite is causing this issue? I suspect it is __vm_enough_memory called from do_brk or mmap_region in Andrey's test case. Tim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org