From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id B07EC6B0044 for ; Fri, 18 Dec 2009 09:09:55 -0500 (EST) Message-ID: <4B2B8D2A.1020804@redhat.com> Date: Fri, 18 Dec 2009 09:09:46 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH v2] vmscan: limit concurrent reclaimers in shrink_zone References: <20091217193818.9FA9.A69D9226@jp.fujitsu.com> <4B2A22C0.8080001@redhat.com> <20091218184046.6547.A69D9226@jp.fujitsu.com> In-Reply-To: <20091218184046.6547.A69D9226@jp.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: lwoodman@redhat.com, LKML , akpm@linux-foundation.org, linux-mm List-ID: On 12/18/2009 05:27 AM, KOSAKI Motohiro wrote: >> KOSAKI Motohiro wrote: >> Finally, having said all that, the system still struggles reclaiming >> memory with >> ~10000 processes trying at the same time, you fix one bottleneck and it >> moves >> somewhere else. The latest run showed all but one running process >> spinning in >> page_lock_anon_vma() trying for the anon_vma_lock. I noticed that there >> are >> ~5000 vma's linked to one anon_vma, this seems excessive!!! >> >> I changed the anon_vma->lock to a rwlock_t and page_lock_anon_vma() to use >> read_lock() so multiple callers could execute the page_reference_anon code. >> This seems to help quite a bit. > > Ug. no. rw-spinlock is evil. please don't use it. rw-spinlock has bad > performance characteristics, plenty read_lock block write_lock for very > long time. > > and I would like to confirm one thing. anon_vma design didn't change > for long year. Is this really performance regression? Do we strike > right regression point? In 2.6.9 and 2.6.18 the system would hit different contention points before getting to the anon_vma lock. Now that we've gotten the other contention points out of the way, this one has finally been exposed. -- 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/ . Don't email: email@kvack.org