Messages in this thread | | | Date | Sat, 26 Oct 2013 12:36:52 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf, x86: Optimize intel_pmu_pebs_fixup_ip() |
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* Don Zickus <dzickus@redhat.com> wrote:
> On Thu, Oct 24, 2013 at 12:52:06PM +0200, Peter Zijlstra wrote: > > On Wed, Oct 23, 2013 at 10:48:38PM +0200, Peter Zijlstra wrote: > > > I'll also make sure to test we actually hit the fault path > > > by concurrently running something like: > > > > > > while :; echo 1 > /proc/sys/vm/drop_caches ; done > > > > > > while doing perf top or so.. > > > > So the below appears to work; I've ran: > > > > while :; do echo 1 > /proc/sys/vm/drop_caches; sleep 1; done & > > while :; do make O=defconfig-build/ clean; perf record -a -g fp -e cycles:pp make O=defconfig-build/ -s -j64; done > > > > And verified that the if (in_nmi()) trace_printk() was visible in the > > trace output verifying we indeed took the fault from the NMI code. > > > > I've had this running for ~ 30 minutes or so and the machine is still > > healthy. > > > > Don, can you give this stuff a spin on your system? > > Hi Peter, > > I finally had a chance to run this on my machine. From my > testing, it looks good. Better performance numbers. I think my > longest latency went from 300K cycles down to 150K cycles and very > few of those (most are under 100K cycles).
Btw., do we know where those ~100k-150k cycles are spent specifically? 100k cycles is still an awful lot of time to spend in NMI context ...
Thanks,
Ingo
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