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author | Gleb Natapov <gleb@redhat.com> | 2011-11-27 17:59:09 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2011-12-06 08:34:02 +0100 |
commit | b202952075f62603bea9bfb6ebc6b0420db11949 (patch) | |
tree | 9c8e0538b455e68b5c371caba5b1585ed0ef9d8a /include/linux/virtio_ids.h | |
parent | b79387ef185af2323594920923cecba5753c3817 (diff) | |
download | op-kernel-dev-b202952075f62603bea9bfb6ebc6b0420db11949.zip op-kernel-dev-b202952075f62603bea9bfb6ebc6b0420db11949.tar.gz |
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 <gleb@redhat.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111127155909.GO2557@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux/virtio_ids.h')
0 files changed, 0 insertions, 0 deletions