From: Gleb Natapov Date: Sun, 27 Nov 2011 15:59:09 +0000 (+0200) Subject: perf, core: Rate limit perf_sched_events jump_label patching X-Git-Tag: v3.3-rc1~192^2~37 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b202952075f62603bea9bfb6ebc6b0420db11949;p=pandora-kernel.git perf, core: Rate limit perf_sched_events jump_label patching jump_lable patching is very expensive operation that involves pausing all cpus. The patching of perf_sched_events jump_label is easily controllable from userspace by unprivileged user. When te user runs a loop like this: "while true; do perf stat -e cycles true; done" ... the performance of my test application that just increments a counter for one second drops by 4%. This is on a 16 cpu box with my test application using only one of them. An impact on a real server doing real work will be worse. Performance of KVM PMU drops nearly 50% due to jump_lable for "perf record" since KVM PMU implementation creates and destroys perf event frequently. This patch introduces a way to rate limit jump_label patching and uses it to fix the above problem. I believe that as jump_label use will spread the problem will become more common and thus solving it in a generic code is appropriate. Also fixing it in the perf code would result in moving jump_label accounting logic to perf code with all the ifdefs in case of JUMP_LABEL=n kernel. With this patch all details are nicely hidden inside jump_label code. Signed-off-by: Gleb Natapov Acked-by: Jason Baron Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20111127155909.GO2557@redhat.com Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed