Tim Bird @ Fri, 13 Jun 2008 12:06:05 -0700: > 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. And what kinds of source/kconfig changes are made for every build? (any versions, e.g. localversion, .version, aren't important, they are for modules ko and vmlinux, afaik) [...] > 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?) kbuild is `ccache` on itself. Every *.o.cmd is kind of info `ccache` hashes (except things like stderr, gcc version) to check repeated rebuilds. Also kconfig<->kbuild link via header magic may confuse general-purpose `ccache`. For rebuilds of the same codebase, it's better to use separate kbuild object output directories. > Any tips would be appreciated. Just my handwaving, but test with couple core config symbols toggling, shows only one `ccache` hit. olecom@flower:/mnt/zdev0/blinux$ CCACHE_DIR=_ccache/ ccache -s cache directory _ccache/ cache hit 1133 cache miss 1141 called for link 28 not a C/C++ file 64 no input file 282 files in cache 2282 cache size 15.7 Mbytes max cache size 976.6 Mbytes olecom@flower:/mnt/zdev0/blinux$ make menuconfig # toggle olecom@flower:/mnt/zdev0/blinux$ diff -u1 .config.old .config --- .config.old 2008-06-13 22:52:37.000000000 +0200 +++ .config 2008-06-13 23:01:07.000000000 +0200 @@ -3,3 +3,3 @@ # Linux kernel version: 2.6.24 -# Fri Jun 13 22:52:37 2008 +# Fri Jun 13 23:01:07 2008 # @@ -67,3 +67,4 @@ CONFIG_POSIX_MQUEUE=y -# CONFIG_BSD_PROCESS_ACCT is not set +CONFIG_BSD_PROCESS_ACCT=y +CONFIG_BSD_PROCESS_ACCT_V3=y # CONFIG_TASKSTATS is not set olecom@flower:/mnt/zdev0/blinux$ olecom@flower:/mnt/zdev0/blinux$ CCACHE_DIR=_ccache/ ccache -s cache directory _ccache/ cache hit 1134 cache miss 1879 called for link 33 not a C/C++ file 79 no input file 401 files in cache 3758 cache size 28.1 Mbytes max cache size 976.6 Mbytes olecom@flower:/mnt/zdev0/blinux$ -- sed 'sed && sh + olecom = love' << '' -o--=O`C #oo'L O <___=E M -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
