Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756699Ab0GURjX (ORCPT ); Wed, 21 Jul 2010 13:39:23 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:52521 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753346Ab0GURjV convert rfc822-to-8bit (ORCPT ); Wed, 21 Jul 2010 13:39:21 -0400 MIME-Version: 1.0 Message-ID: <6433bf44-2a68-485a-b048-a7aca241677d@default> Date: Wed, 21 Jul 2010 10:37:20 -0700 (PDT) From: Dan Magenheimer To: ngupta@vflare.org Cc: Pekka Enberg , Hugh Dickins , Andrew Morton , Greg KH , Rik van Riel , Avi Kivity , Christoph Hellwig , Minchan Kim , Konrad Wilk , linux-mm , linux-kernel Subject: RE: [PATCH 0/8] zcache: page cache compression support References: <1279283870-18549-1-git-send-email-ngupta@vflare.org> <4f986c65-c17e-47d8-9c30-60cd17809cbb@default> <4C45A9BA.1090903@vflare.org> <9e4cae1f-c102-43ea-9ba0-611c8ad68c9b@default 4C46772E.3000500@vflare.org> In-Reply-To: <4C46772E.3000500@vflare.org> X-Priority: 3 X-Mailer: Oracle Beehive Extensions for Outlook 2.0.1.2.1.2 (406224) [OL 12.0.6535.5005] Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT X-Source-IP: acsmt354.oracle.com [141.146.40.154] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090208.4C473067.0218:SCFMA4539814,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1161 Lines: 24 > > Maybe the best solution is to make the threshold a sysfs > > settable? Or maybe BOTH the single-page threshold and > > the average threshold as two different sysfs settables? > > E.g. throw away a put page if either it compresses poorly > > or adding it to the pool would push the average over. > > Considering overall compression average instead of bothering about > individual page compressibility seems like a good point. Still, I think > storing completely incompressible pages isn't desirable. > > So, I agree with the idea of separate sysfs tunables for average and > single-page > compression thresholds with defaults conservatively set to 50% and > PAGE_SIZE/2 > respectively. I will include these in "v2" patches. Unless the single-page compression threshold is higher than the average, the average is useless. IMHO I'd suggest at least 5*PAGE_SIZE/8 as the single-page threshold, possibly higher. -- 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/