From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754002Ab1H2PJd (ORCPT ); Mon, 29 Aug 2011 11:09:33 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:25045 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753946Ab1H2PJ3 convert rfc822-to-8bit (ORCPT ); Mon, 29 Aug 2011 11:09:29 -0400 MIME-Version: 1.0 Message-ID: <4724822e-3798-4837-aba3-e87d191bd40e@default> Date: Mon, 29 Aug 2011 08:08:32 -0700 (PDT) From: Dan Magenheimer To: Nebojsa Trpkovic Cc: linux-kernel@vger.kernel.org, Konrad Wilk , Andrew Morton , Seth Jennings , Nitin Gupta Subject: RE: cleancache can lead to serious performance degradation References: <4E4C395E.20000@gmail.com> <20110825041212.GA5014@dumpdata.com> <3aef71a8-d390-4a91-bfef-561c89edc040@default 4E5AE138.20408@gmail.com> In-Reply-To: <4E5AE138.20408@gmail.com> X-Priority: 3 X-Mailer: Oracle Beehive Extensions for Outlook 2.0.1.4.1.0 (410211) [OL 12.0.6557.5001] Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT X-Source-IP: acsinet21.oracle.com [141.146.126.237] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090201.4E5BAB7E.013C:SCFMA922111,ss=1,re=-4.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Nebojsa Trpkovic [mailto:trx.lists@gmail.com] > Subject: Re: cleancache can lead to serious performance degradation > > Thank you everybody for reviewing my report. Thanks for reporting it! To paraphrase Clint Eastwood: "A kernel developer's got to know his patchset's limitations". (Clint said "A man's got to know his limitations" in Magnum Force, 1973.) > I've noticed performance degradation during the real workload. I did not > run any special benchmarks to prove this problem. All my conclusions are > based on everyday usage case scenarios. > > I use multi-purpose (read: all-purpose) server with Intel Core 2 Duo > E6550, 8GB DDR2, 4 1Gbps NICs and 16 1.5TB 5.4k rpm hard drives in LAN > with ~50 workstations and WAN with couple of hundreds clients. OK, so the old CPU is mostly acting as a fancy router between 16 spindles and 4 fast NICs to transfer very large "packets" (sequential files). I can see how that kind of workload would not be kind to zcache, though a more modern multi-core (4-core i7?) might handle it better. And, as suggested earlier in this thread, a faster-but-less-space-efficient compression algorithm would be useful too, along with some policy that senses when > Last but not least, thank you for developing such a great feature for > Linux kernel! Thanks! Many people contributed (especially Nitin Gupta). I hope other users and workloads have better luck with it than you/yours does! > Best Regards, > Nebojsa Trpkovic Thanks, Dan