From mboxrd@z Thu Jan 1 00:00:00 1970 From: "J. R. Okajima" Subject: Re: Q. cache in squashfs? Date: Sun, 11 Jul 2010 14:55:14 +0900 Message-ID: <6909.1278827714@jrobl> References: <19486.1277347066@jrobl> <4C354CBE.70401@lougher.demon.co.uk> <6356.1278569327@jrobl> <15323.1278662033@jrobl> <4C36FAB1.6010506@lougher.demon.co.uk> <4C370017.4070604@lougher.demon.co.uk> <7545.1278738474@jrobl> <4C3930E9.8080905@lougher.demon.co.uk> Cc: linux-fsdevel@vger.kernel.org To: Phillip Lougher Return-path: Received: from mtoichi14.ns.itscom.net ([219.110.2.184]:37251 "EHLO mtoichi14.ns.itscom.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750797Ab0GKFzj (ORCPT ); Sun, 11 Jul 2010 01:55:39 -0400 In-Reply-To: <4C3930E9.8080905@lougher.demon.co.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Phillip Lougher: > In your first column (ext3 on squashfs), only a small amount of the > overall cost is being accounted to the 'cat10' command, the bulk of > the work is being accounted to the kernel 'loop1' thread and this isn't > showing up. In the other cases (Squashfs only) the entire cost is being > accounted to the 'cat10' command. The resulting results are therefore > completely bogus, and incorrectly show higher CPU usage for Squashfs. Ah, I forget about the kthread. My question about CPU usage must be due to the kthread. Also I could confirm that the sequential access pattern as you did shows good performance. While the very random access shows worse, it is a positive effect of loopback caching as you wrote in your first reply. Thank you very much. J. R. Okajima