From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx137.postini.com [74.125.245.137]) by kanga.kvack.org (Postfix) with SMTP id 977C16B004D for ; Thu, 10 May 2012 18:30:55 -0400 (EDT) Message-ID: <4FAC418E.6060500@redhat.com> Date: Thu, 10 May 2012 18:30:38 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 1/1] mlock: split the shmlock_user_lock spinlock into per user_struct spinlock References: <1336066477-3964-1-git-send-email-rajman.mekaco@gmail.com> <4FA2C946.60006@redhat.com> <4FA2EA4A.6040703@redhat.com> <4FABD6BE.1060401@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: rajman mekaco Cc: Ingo Molnar , Peter Zijlstra , Paul Gortmaker , Andrew Morton , KOSAKI Motohiro , Minchan Kim , Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org On 05/10/2012 11:39 AM, rajman mekaco wrote: > On Thu, May 10, 2012 at 8:24 PM, Rik van Riel wrote: >> On 05/10/2012 09:34 AM, rajman mekaco wrote: >> >>> Any updates on this ? >> >> >> There is still no usecase to demonstrate a problem, so no real >> justification to merge the patch. Coming up with such a usecase >> is up to the submitter of the patch. > > Maybe you didn't read my last email: > If 2 different user-mode processes executing on 2 CPUs under 2 different > users want to access the same shared memory through the > shmctl(SHM_LOCK) / shmget(SHM_HUGETLB) / usr_shm_lock > primitives, they could compete/spin even though their user_structs > are different. > > Can you please correct me if I am missing some crucial point of understanding ? Mlock is a very very expensive operation. Updating the mlock statistics is a very cheap operation. Does this spinlock ever show up contention wise? -- All rights reversed -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org