From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lazybastard.de ([212.112.238.170]:60258 "EHLO longford.logfs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758689AbYFOR6s (ORCPT ); Sun, 15 Jun 2008 13:58:48 -0400 Date: Sun, 15 Jun 2008 19:58:35 +0200 From: =?utf-8?B?SsO2cm4=?= Engel Subject: Re: Not as much ccache win as I expected Message-ID: <20080615175835.GA15244@logfs.org> References: <4852C51D.30206@am.sony.com> <8499950a0806131354u7d2431b2n2df50b7b6c98f18d@mail.gmail.com> <4852E245.4020502@am.sony.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4852E245.4020502@am.sony.com> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Tim Bird Cc: Oleg Verych , linux-embedded , linux-kbuild@vger.kernel.org On Fri, 13 June 2008 14:10:29 -0700, Tim Bird wrote: > > Maybe I should just be grateful for any ccache hits I get. ccache's usefulness depends on your workload. If you make a change to include/linux/fs.h, close to 100% of the kernel is rebuilt, with or without ccache. But when you revert that change, the build time differs dramatically. Without ccache, fs.h was simply changed again and everything is rebuild. With ccache, there are hits for the old version and all is pulled from the cache - provided you have allotted enough disk for it. If you never revert to an old version or do some equivalent operation, ccache can even be a net loss. On a fast machine, the additional disk accesses are easily more expensive than the minimal cpu gains. Jörn -- Public Domain - Free as in Beer General Public - Free as in Speech BSD License - Free as in Enterprise Shared Source - Free as in "Work will make you..."