On Sat, Oct 26, 2013 at 12:36:52PM +0200, Ingo Molnar wrote: > > * Don Zickus <dzic...@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 ...
I agree, there is still a bunch of latency in the nmi path. I believe it is still in the pebs code. I share the machine with a colleague right now, so I haven't been able to isolate it. But going from a few hundred samples over a million cycles to about a couple dozen over 100K was a big step. :-) I still see perf throttling and people are complaining about it here so I still plan to keep investigating. Just taking me a while. Sorry about that. Cheers, Don -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
