From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 4A9036B025F for ; Tue, 25 Jul 2017 12:04:05 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id l3so28878062wrc.12 for ; Tue, 25 Jul 2017 09:04:05 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 9si15724639wra.123.2017.07.25.09.04.03 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 25 Jul 2017 09:04:04 -0700 (PDT) Date: Tue, 25 Jul 2017 18:04:00 +0200 From: Michal Hocko Subject: Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Message-ID: <20170725160359.GO26723@dhcp22.suse.cz> References: <20170724072332.31903-1-mhocko@kernel.org> <20170724140008.sd2n6af6izjyjtda@node.shutemov.name> <20170724141526.GM25221@dhcp22.suse.cz> <20170724145142.i5xqpie3joyxbnck@node.shutemov.name> <20170724161146.GQ25221@dhcp22.suse.cz> <20170725142626.GJ26723@dhcp22.suse.cz> <20170725151754.3txp44a2kbffsxdg@node.shutemov.name> <20170725152300.GM26723@dhcp22.suse.cz> <20170725153110.qzfz7wpnxkjwh5bc@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170725153110.qzfz7wpnxkjwh5bc@node.shutemov.name> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Andrew Morton , David Rientjes , Tetsuo Handa , Oleg Nesterov , Hugh Dickins , Andrea Arcangeli , linux-mm@kvack.org, LKML On Tue 25-07-17 18:31:10, Kirill A. Shutemov wrote: > On Tue, Jul 25, 2017 at 05:23:00PM +0200, Michal Hocko wrote: > > what is stdev? > > Updated tables: > > 3 runs before the patch: > Min. 1st Qu. Median Mean 3rd Qu. Max. Stdev > 177200 205000 212900 217800 223700 2377000 32868 > 172400 201700 209700 214300 220600 1343000 31191 > 175700 203800 212300 217100 223000 1061000 31195 > > 3 runs after the patch: > Min. 1st Qu. Median Mean 3rd Qu. Max. Stdev > 175900 204800 213000 216400 223600 1989000 27210 > 180300 210900 219600 223600 230200 3184000 32609 > 182100 212500 222000 226200 232700 1473000 32138 High std/avg ~15% matches my measurements (mine were even higher ~20%) and that would suggest that 3% average difference is still somehing within a "noise". Anyway, I do not really need to take the lock unless the task is the oom victim. Could you try whether those numbers improve if the lock is conditional? Thanks! --- diff --git a/mm/mmap.c b/mm/mmap.c index 0eeb658caa30..ca8a274485f8 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -44,6 +44,7 @@ #include #include #include +#include #include #include @@ -2997,7 +2998,8 @@ void exit_mmap(struct mm_struct *mm) * oom reaper might race with exit_mmap so make sure we won't free * page tables or unmap VMAs under its feet */ - down_write(&mm->mmap_sem); + if (tsk_is_oom_victim(current)) + down_write(&mm->mmap_sem); free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING); tlb_finish_mmu(&tlb, 0, -1); @@ -3012,7 +3014,8 @@ void exit_mmap(struct mm_struct *mm) } mm->mmap = NULL; vm_unacct_memory(nr_accounted); - up_write(&mm->mmap_sem); + if (tsk_is_oom_victim(current)) + up_write(&mm->mmap_sem); } /* Insert vm structure into process list sorted by address -- Michal Hocko SUSE Labs -- 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