From mboxrd@z Thu Jan 1 00:00:00 1970 From: Milian Wolff Subject: Re: Perf report --percentage Date: Wed, 08 Jun 2016 09:34:58 +0200 Message-ID: <1936512.XMEGsyMYkf@agathebauer> References: <6076A35470B38B408600AA0E3B4A31E767471A9E@ORSMSX114.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1514564.IiiRmWJGRA"; micalg="sha1"; protocol="application/pkcs7-signature" Return-path: Received: from mail.kdab.com ([176.9.126.58]:60685 "EHLO mail.kdab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751220AbcFHHfF (ORCPT ); Wed, 8 Jun 2016 03:35:05 -0400 In-Reply-To: <6076A35470B38B408600AA0E3B4A31E767471A9E@ORSMSX114.amr.corp.intel.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: shiny.sebastian@intel.com Cc: linux-perf-users@vger.kernel.org --nextPart1514564.IiiRmWJGRA Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Dienstag, 7. Juni 2016 19:21:15 CEST Sebastian, Shiny wrote: > Hi, > > I work with Intel and am running perf tool within Linux VMs on Windows > Hyper-V. With kernel 4.6 and corresponding perf version, percentages of > call stacks at deeper levels do not seem to add up to 100% or parent value > (26.97%): example below. I have tried the -percentage flag with both > 'absolute' and 'relative' values and they don't seem to change the output > at all. Is this a bug or something wrong with my perf flags ? > > Commands used: > #perf record -a -g -c 10000 sleep 10 > #perf report -i cpu3.data.old -C 1 --no-children > > - 27.48% fio [kernel.kallsyms] [k] __softirqentry_text_start > __softirqentry_text_start > - irq_exit > - 26.97% smp_call_function_single_interrupt > - call_function_single_interrupt > + 4.21% __blk_run_queue > + 4.09% hv_ringbuffer_write > + 1.83% 0x99c > + 1.78% __blockdev_direct_IO > + 0.96% do_blockdev_direct_IO > + 0.95% generic_make_request > + 0.86% blk_queue_bio > + 0.70% iov_iter_get_pages > + 0.64% md_make_request > + 0.55% do_io_submit > 0.51% entry_SYSCALL_64_fastpath > + 0.51% hyperv_vector_handler Can you try to look at the output of perf report -i cpu3.data.old -C 1 --no-children -g graph,0 i.e. potentially there are more entries with a cost of 0.5% or less, which by default falls below the threshold. That said, I just tested it and it doesn't work for me either: tmp$ perf record --call-graph dwarf kwrite [ perf record: Woken up 65 times to write data ] [ perf record: Captured and wrote 16.308 MB perf.data (2032 samples) ] tmp$ perf report -g graph,0 --no-children - 9.47% kwrite ld-2.23.so [.] do_lookup_x - 2.21% do_lookup_x - _dl_lookup_symbol_x + 1.42% _dl_relocate_object + 0.74% _dl_fixup + 7.06% kwrite ld-2.23.so [.] strcmp It's also bogus when I look at it with --children: - 10.76% 9.47% kwrite ld-2.23.so [.] do_lookup_x + 1.54% _start + 1.34% do_lookup_x + 0.61% _dl_runtime_resolve_avx - 7.06% 7.06% kwrite ld-2.23.so [.] strcmp + 0.42% _start + 0.22% _dl_runtime_resolve_avx So someone else with more insight should answer whether this output can be explained somehow. > Older version: Perf version 4.2 on kernel 4.2 - seems to normalize them to > 100%. 27.69% swapper [kernel.kallsyms] [k] intel_idle > > ---intel_idle > > |--99.84%-- cpuidle_enter_state > | > | cpuidle_enter > | call_cpuidle > | cpu_startup_entry > | > | |--97.27%-- start_secondary > | | > | --2.73%-- rest_init > | > | start_kernel > | x86_64_start_reservations > | x86_64_start_kernel > > --0.16%-- [...] This output can be reproduced on newer perf by passing `-g fractal` to `perf report`. I still get the issues as shown above though with a newer perf: - 9.47% kwrite ld-2.23.so [.] do_lookup_x + 23.31% do_lookup_x - 7.06% kwrite ld-2.23.so [.] strcmp + 9.06% strcmp + 5.71% kwrite ld-2.23.so [.] check_match I.e. ~74% and 91% of the samples don't seen to have a proper backtrace attribution? Cheers -- Milian Wolff | milian.wolff@kdab.com | Software Engineer KDAB (Deutschland) GmbH&Co KG, a KDAB Group company Tel: +49-30-521325470 KDAB - The Qt Experts --nextPart1514564.IiiRmWJGRA Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIUdzCCBGYw ggNOoAMCAQICEFEmCpMc4n+cw6VfeeByroIwDQYJKoZIhvcNAQEFBQAwgZMxCzAJBgNVBAYTAlVT MQswCQYDVQQIEwJVVDEXMBUGA1UEBxMOU2FsdCBMYWtlIENpdHkxHjAcBgNVBAoTFVRoZSBVU0VS VFJVU1QgTmV0d29yazEhMB8GA1UECxMYaHR0cDovL3d3dy51c2VydHJ1c3QuY29tMRswGQYDVQQD ExJVVE4gLSBEQVRBQ29ycCBTR0MwHhcNMDUwNjA3MDgwOTEwWhcNMTkwNjI0MTkwNjMwWjBvMQsw CQYDVQQGEwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVy bmFsIFRUUCBOZXR3b3JrMSIwIAYDVQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290MIIBIjAN BgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAt/caM+byAAQtOeBOW+0fvGwPzbX6I7bO3psRM5ek 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