From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 5524C6B00FA for ; Thu, 11 Mar 2010 18:41:56 -0500 (EST) Date: Thu, 11 Mar 2010 15:41:24 -0800 From: Andrew Morton Subject: Re: [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure Message-Id: <20100311154124.e1e23900.akpm@linux-foundation.org> In-Reply-To: <1268048904-19397-1-git-send-email-mel@csn.ul.ie> References: <1268048904-19397-1-git-send-email-mel@csn.ul.ie> 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: linux-mm@kvack.org, Nick Piggin , Christian Ehrhardt , Chris Mason , Jens Axboe , linux-kernel@vger.kernel.org List-ID: On Mon, 8 Mar 2010 11:48:20 +0000 Mel Gorman wrote: > Under memory pressure, the page allocator and kswapd can go to sleep using > congestion_wait(). In two of these cases, it may not be the appropriate > action as congestion may not be the problem. clear_bdi_congested() is called each time a write completes and the queue is below the congestion threshold. So if the page allocator or kswapd call congestion_wait() against a non-congested queue, they'll wake up on the very next write completion. Hence the above-quoted claim seems to me to be a significant mis-analysis and perhaps explains why the patchset didn't seem to help anything? -- 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