Hi Ingo, On Mon, Mar 23, 2015 at 08:22:14AM +0100, Ingo Molnar wrote: > > * Namhyung Kim <[email protected]> wrote: > > > Currently the build-id only recorded for sampled location, but in > > order to correctly view/annotate callchains it might need the > > build-id's of callchains too. I guess this choice was due to a > > performance impact on the post-processing at perf record time. > > > > Add a new option --buildid-callchain to record this info. > > > > $ perf record -o xxx -g -- perf > /dev/null > > $ perf buildid-list -i xxx > > 6ebcee76c4b04895598b4df86ec445c49fc137a2 > > /lib/modules/3.18.6-1-ARCH/build/vmlinux > > fc0759b71584d2513b04f1b530965a61b5e499e2 /usr/lib/ld-2.21.so > > > > $ perf record -o yyy -g --buildid-callchain -- perf > /dev/null > > $ perf buildid-list -i yyy > > 6ebcee76c4b04895598b4df86ec445c49fc137a2 > > /lib/modules/3.18.6-1-ARCH/build/vmlinux > > 4235ae90856f98d2746529648a3339ebfa6ede43 > > /home/namhyung/project/linux/tools/perf/perf > > fc0759b71584d2513b04f1b530965a61b5e499e2 /usr/lib/ld-2.21.so > > 9ac81172d5ff96f40d984fe7c10073a98f1a6b2e /usr/lib/libc-2.21.so > > 864583bb881db1d260660a30a51b3f5022cd538b /usr/lib/libnuma.so.1.0.0 > > Just curious, could you try to measure the performance impact of this > change?
$ time perf record --call-graph dwarf -o kbuild.xxx -a -- sleep 30 [ perf record: Woken up 34674 times to write data ] [ perf record: Captured and wrote 9538.729 MB kbuild.xxx (1211997 samples) ] real 0m32.244s user 0m1.097s sys 0m8.997s $ time perf record --call-graph dwarf -o kbuild.yyy --buildid-callchain -a -- sleep 30 [ perf record: Woken up 40902 times to write data ] [ perf record: Captured and wrote 11208.500 MB kbuild.yyy (1433922 samples) ] real 2m21.695s user 1m33.127s sys 0m22.077s > > Also, unless the performance (or file size) effect is horrible, I > think this flag should be implicitly set by -g. Agreed. But unfortunately, it seems horrible. ;-p > > 99.999% of users won't know about this flag, and will see broken > annotations! Well, most of them will see correct one unless the binary is changed in the meantime. :) Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
