Messages in this thread | | | Date | Wed, 27 May 2015 11:04:39 +0200 | From | Martin Liška <> | Subject | Re: [RFC] Add --show-total-period for perf annotate |
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On 05/27/2015 10:46 AM, Martin Liška wrote: > On 05/26/2015 07:03 PM, Andi Kleen wrote: >>> Anyway, attached patch is capable of displaying milliseconds approximation for each instruction. >> >> You realize that the events perf is not counting do not directly map to >> wall time? Even if you count cycles, the cycles are either stopping in idle >> or changing unit as the CPU's frequencies change. For other events the >> relationship is even more remote, think what happens when counting cache or >> TLB misses. >> >> Also even if it was mapping to time somehow, it's just a hit, not a >> duration, so it cannot say how long a individual instruction took. >> >> So you cannot map a sample event to time. >> >> To do what you want you would need to use something like processor >> trace, which can do exact accounting. >> >> I think the only thing that makes sense is to account it relative to >> the event counts. >> >> -Andi >> > > Hello Andi. > > I realize all aspects and capabilities of perf infrastructure. Even though > these numbers are not precise, I helped me a lot with debugging of a benchmark > which heavily utilizes a single CPU and runs in magnitude of seconds. > > Ok, so let's convert the patch to feature that we can map an instruction > to a percentage number of events (cycles) it takes. > > If I understand correctly, is it just about division of the number of events > related to an instruction and total number of events? > > Thanks, > Martin > > -- > To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi.
Sample output to verify that we have the same idea in mind:
$ perf annotate --show-total-period
Disassembly of section .text: : : 0000000000038890 <random_r>: : __random_r(): 1695 : 38890: test %rdi,%rdi 0 : 38893: je 38918 <random_r+0x88> 1 : 38899: test %rsi,%rsi 0 : 3889c: je 38918 <random_r+0x88> 9 : 3889e: mov 0x18(%rdi),%eax 1833 : 388a1: mov 0x10(%rdi),%rdx 2 : 388a5: test %eax,%eax 0 : 388a7: je 388f8 <random_r+0x68> 168 : 388a9: mov (%rdi),%rcx 8 : 388ac: mov 0x8(%rdi),%r8 1325 : 388b0: mov 0x28(%rdi),%r9
Where: $ perf report | head
# To display the perf.data header info, please use --header/--header-only options. # # Samples: 44K of event 'cycles' # Event count (approx.): 42988831618
Thank for ideas, Martin
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