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 8BCF96B005D for ; Tue, 11 Aug 2009 19:32:51 -0400 (EDT) Date: Wed, 12 Aug 2009 08:31:03 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 3/6] tracing, page-allocator: Add trace event for page traffic related to the buddy lists In-Reply-To: <1249918915-16061-4-git-send-email-mel@csn.ul.ie> References: <1249918915-16061-1-git-send-email-mel@csn.ul.ie> <1249918915-16061-4-git-send-email-mel@csn.ul.ie> Message-Id: <20090811164030.9AE2.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: kosaki.motohiro@jp.fujitsu.com, Larry Woodman , Ingo Molnar , Andrew Morton , riel@redhat.com, Peter Zijlstra , Li Ming Chun , LKML , linux-mm@kvack.org List-ID: > The page allocation trace event reports that a page was successfully allocated > but it does not specify where it came from. When analysing performance, > it can be important to distinguish between pages coming from the per-cpu > allocator and pages coming from the buddy lists as the latter requires the > zone lock to the taken and more data structures to be examined. > > This patch adds a trace event for __rmqueue reporting when a page is being > allocated from the buddy lists. It distinguishes between being called > to refill the per-cpu lists or whether it is a high-order allocation. > Similarly, this patch adds an event to catch when the PCP lists are being > drained a little and pages are going back to the buddy lists. > > This is trickier to draw conclusions from but high activity on those > events could explain why there were a large number of cache misses on a > page-allocator-intensive workload. The coalescing and splitting of buddies > involves a lot of writing of page metadata and cache line bounces not to > mention the acquisition of an interrupt-safe lock necessary to enter this > path. Looks good to me. Reviewed-by: KOSAKI Motohiro -- 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