From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx199.postini.com [74.125.245.199]) by kanga.kvack.org (Postfix) with SMTP id 267566B0032 for ; Tue, 23 Jul 2013 03:05:11 -0400 (EDT) Received: by mail-ob0-f195.google.com with SMTP id eh20so1962363obb.2 for ; Tue, 23 Jul 2013 00:05:10 -0700 (PDT) Message-ID: <51EE2B16.3020605@gmail.com> Date: Tue, 23 Jul 2013 15:04:54 +0800 From: Hush Bensen MIME-Version: 1.0 Subject: Re: [PATCH] hugepage: allow parallelization of the hugepage fault path References: <1373671681.2448.10.camel@buesod1.americas.hpqcorp.net> <1373858204.13826.9.camel@buesod1.americas.hpqcorp.net> <20130715072432.GA28053@voom.fritz.box> <20130715160802.9d0cdc0ee012b5e119317a98@linux-foundation.org> <1374090625.15271.2.camel@buesod1.americas.hpqcorp.net> <20130718090719.GB9761@lge.com> In-Reply-To: <20130718090719.GB9761@lge.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Davidlohr Bueso , Andrew Morton , David Gibson , Hugh Dickins , Rik van Riel , Michel Lespinasse , Mel Gorman , Konstantin Khlebnikov , Michal Hocko , "AneeshKumarK.V" , KAMEZAWA Hiroyuki , Hillf Danton , linux-mm@kvack.org, LKML , Eric B Munson , Anton Blanchard On 07/18/2013 05:07 PM, Joonsoo Kim wrote: > On Wed, Jul 17, 2013 at 12:50:25PM -0700, Davidlohr Bueso wrote: > >> From: Davidlohr Bueso >> >> - Cleaned up and forward ported to Linus' latest. >> - Cache aligned mutexes. >> - Keep non SMP systems using a single mutex. >> >> It was found that this mutex can become quite contended >> during the early phases of large databases which make use of huge pages - for instance >> startup and initial runs. One clear example is a 1.5Gb Oracle database, where lockstat >> reports that this mutex can be one of the top 5 most contended locks in the kernel during >> the first few minutes: >> >> hugetlb_instantiation_mutex: 10678 10678 >> --------------------------- >> hugetlb_instantiation_mutex 10678 [] hugetlb_fault+0x9e/0x340 >> --------------------------- >> hugetlb_instantiation_mutex 10678 [] hugetlb_fault+0x9e/0x340 >> >> contentions: 10678 >> acquisitions: 99476 >> waittime-total: 76888911.01 us > Hello, > I have a question :) > > So, each contention takes 7.6 ms in your result. > Do you map this area with VM_NORESERVE? > If we map with VM_RESERVE, when page fault, we just dequeue a huge page from a queue and clear > a page and then map it to a page table. So I guess, it shouldn't take so long. I don't think there is clear page operation after dequeue huge page, actually it's even not done during hugetlb_reserve_pages, do you know why? There is just clear operation in hugetlb_no_page. > I'm wondering why it takes so long. > > And do you use 16KB-size hugepage? > If so, region handling could takes some times. If you access the area as random order, > the number of region can be more than 90000. I guess, this can be one reason to too long > waittime. > > Thanks. > > -- > 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 -- 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