From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Bird Subject: Not as much ccache win as I expected Date: Fri, 13 Jun 2008 12:06:05 -0700 Message-ID: <4852C51D.30206@am.sony.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Sender: linux-embedded-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: linux-embedded Cc: linux-kbuild@vger.kernel.org I'm running an automated test which does numerous compiles of the Linux kernel. One of the things I do is create a localversion file at the root of the kernel source tree with a unique identifier that I use later on in testing. I started using ccache to improve the performance of my builds, but found that the hit rate on the cache was not very good. $ ccache -s cache directory /home/tbird/.ccache cache hit 74416 cache miss 59400 called for link 87252 compile failed 21 not a C/C++ file 143449 no input file 49336 files in cache 42844 cache size 1.8 Gbytes max cache size 2.0 Gbytes Thinking that the problem might be having a unique version for every build (and that this change flowed to every file via the version.h file), I tried building without this change. I saw an improvement, but not much. Is there anything else obvious which is prevents ccache from working well with a kernel build (that is, anything else that would, for otherwise identical C files with a similar build, cause a difference?) Any tips would be appreciated. -- Tim ============================= Tim Bird Architecture Group Chair, CE Linux Forum Senior Staff Engineer, Sony Corporation of America =============================