Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 13 Apr 2012 11:30:52 -0700 | Subject | Re: [tip:perf/core] perf ui annotate browser: Allow toggling addr offset view |
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On Fri, Apr 13, 2012 at 11:25 AM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > <kmem_cache_free>: > 1.91 : push %rbp
Oh, btw, talking about kmem_cache_free: that one uses altinstructions, and so perf report shows the hottest instruction wrong (and I'm not talking about "ugly"):
12.38 : ffffffff810d7ee5: lea (%r8),%rsi 0.71 : ffffffff810d7ee8: callq ffffffff812d3df0 <this_cpu_cmpxchg16b_emu>
that "lea" really isn't very expensive. In reality, it's not "lea+call", it's a "lock ; cmpxchg16b + setz" instruction. But "perf" doesn't know about alternative instructions, and if somebody were to try to teach it, that would be lovely.
Happily, x86-64 doesn't have quite as many of them as x86-32 does. But they are there, sometimes in interesting functions.
Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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