Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 21 Feb 2011 12:54:52 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH] kprobes - do not allow optimized kprobes in entry code |
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On Sun, Feb 20, 2011 at 01:59:48PM +0100, Ingo Molnar wrote: > > * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote: > > > Thanks, I've also tested. (But my machine has no L1-icache-prefetches* support) > > What I can tell is both of L1-icache-load and L1-icache-load-misses is reduced by > > the patch. ;-) > > That's actually a pretty interesting result: it means that compressing entry code > into a single section compresses the icache footprint in a measurable way. The > icache miss rate went down by about 6%: > > > 1,234,272 L1-icache-load-misses ( +- 0.105% ) > > 1,155,816 L1-icache-load-misses ( +- 0.113% ) > > Which, assuming that there's no kernel build and bootup related skew effect that is > larger than 2-3% means that this is an improvement. > > perf feature request: would be nice if it was able to do: > > perf stat --record ... > perf diff > > and it would show a comparison of the two runs. > > In hindsight it makes sense: the patch probably reduced the fragmentation of the > icache for this workload. > > But it's still surprising :-) > > Mind splitting the patch up into two parts, the first one that does the performance > optimization intentionally (with numbers, explanation, etc.), the second one that > uses the new section for kprobes exclusion? np, I'll send v2 shortly
thanks, jirka
> > Thanks, > > Ingo
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