From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 075438D0040 for ; Mon, 28 Mar 2011 12:59:15 -0400 (EDT) From: Andi Kleen Subject: Re: [PATCH]mmap: avoid unnecessary anon_vma lock References: <1301277532.3981.25.camel@sli10-conroe> Date: Mon, 28 Mar 2011 09:57:39 -0700 In-Reply-To: <1301277532.3981.25.camel@sli10-conroe> (Shaohua Li's message of "Mon, 28 Mar 2011 09:58:52 +0800") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: Shaohua Li Cc: Andrew Morton , linux-mm , lkml , Rik van Riel , Hugh Dickins Shaohua Li writes: > If we only change vma->vm_end, we can avoid taking anon_vma lock even 'insert' > isn't NULL, which is the case of split_vma. > From my understanding, we need the lock before because rmap must get the > 'insert' VMA when we adjust old VMA's vm_end (the 'insert' VMA is linked to > anon_vma list in __insert_vm_struct before). > But now this isn't true any more. The 'insert' VMA is already linked to > anon_vma list in __split_vma(with anon_vma_clone()) instead of > __insert_vm_struct. There is no race rmap can't get required VMAs. > So the anon_vma lock is unnecessary, and this can reduce one locking in brk > case and improve scalability. Looks good to me. -Andi -- ak@linux.intel.com -- Speaking for myself only -- 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