Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269200AbUI2XcC (ORCPT ); Wed, 29 Sep 2004 19:32:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269198AbUI2X3x (ORCPT ); Wed, 29 Sep 2004 19:29:53 -0400 Received: from fw.osdl.org ([65.172.181.6]:47232 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S269207AbUI2X3S (ORCPT ); Wed, 29 Sep 2004 19:29:18 -0400 Date: Wed, 29 Sep 2004 16:29:08 -0700 (PDT) From: Judith Lebzelter To: cc: , Subject: OSDL aio-stress results on latest kernels show buffered random read issue Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1320 Lines: 40 Hello; I am running aio-stress on the most recent kernels and have found that on linux-2.6.8, 2.6.9-rc2 and 2.6.9-rc2-mm4 the performance of buffered random reads is poor compared to the buffered random writes: 2.6.8 2.6.9-rc2 2.6.9-rc2-mm4 -------------------------------------------- random write 35.66 MB/s 34.80 MB/s 29.89 MB/s random read 7.69 MB/s 7.50 MB/s 7.68 MB/s ** 2CPU hosts with striped Megaraid. 1G RAM. 4G File. This shows up on our 4CPU host as well. (striped AACRAID.4G RAM. 8G File): 2.6.9-rc2 2.6.9-rc2-mm4 2.6.9-rc2-mm1 ------------------------------------------- random write 31.36 MB/s 18.92 MB/s 18.97 MB/s random read 11.13 MB/s 9.74 MB/s 11.05 MB/s There seems to be an issue with the reads. Usually, reads should be at least as fast as writes of the same type. Also, there seems to be a substantial drop-off in the performance of AIO buffered-random writes in the mm kernels. (14% on 2CPU, 40% on 4CPU) Regards; Judith Lebzelter OSDL - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/