From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Wed, 7 Mar 2012 20:40:03 +0100 Subject: [Buildroot] [pull request] Pull request for branch for-2012.05/ccache-fixes In-Reply-To: References: Message-ID: <20120307204003.3a02b08b@skate> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Hello, Le Wed, 7 Mar 2012 20:26:48 +0100, Thomas Petazzoni a ?crit : > ccache: set COMPILERCHECK to 'none' Some numbers about this. Without the patch, a build of Qt with an empty cache takes the following time: real 8m17.607s user 31m30.830s sys 1m8.990s Without the patch, a build of Qt with a cache full takes the following time: real 8m12.630s user 31m17.340s sys 1m8.520s So basically, no improvement. With the patch, a build of Qt with a cache full takes the following time: real 4m37.559s user 5m13.390s sys 0m31.840s Here, there is clearly a nice impact of ccache. I have decided to take a simpler approach than the one explored by Arnout. Arnout approach was, IMO, too complicated, and only applicable to external toolchains. My approach is simpler, but indeed requires attention from the developer on whether the cache should be invalidated or not. However, I am not sure it is possible to provide a solution that is both safe (in terms of cache contents validity) *and* efficient (in terms of cache usage). Also, the approach taken by my patch is basically the same as what was happening with previous versions of ccache, so this is not a new behaviour. Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com