From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH 5/8] readahead: add /debug/readahead/stats Date: Tue, 22 Nov 2011 00:32:55 +0100 Message-ID: <20111121233255.GF24062@one.firstfloor.org> References: <20111121091819.394895091@intel.com> <20111121093846.636765408@intel.com> <20111121152958.e4fd76d4.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Wu Fengguang , Linux Memory Management List , linux-fsdevel@vger.kernel.org, Ingo Molnar , Jens Axboe , Peter Zijlstra , Rik van Riel , LKML , Andi Kleen To: Andrew Morton Return-path: Content-Disposition: inline In-Reply-To: <20111121152958.e4fd76d4.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org > I may be wrong, but I don't think the CPU cost of this code matters a > lot. People will rarely turn it on and disk IO is a lot slower than > CPU actions and it's waaaaaaay more important to get high-quality info > about readahead than it is to squeeze out a few CPU cycles. In its current form it would cache line bounce, which tends to be extremly slow. But the solution is probably to make it per CPU. -Andi -- 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