From mboxrd@z Thu Jan 1 00:00:00 1970 From: Milian Wolff Subject: Re: Tracing sched_switch events for client application when process is switched back in Date: Wed, 16 Nov 2016 12:17:40 +0100 Message-ID: <3673091.Y7H8VIyPtY@milian-kdab2> References: <10618911.8qrkJBTkNF@milian-kdab2> <2210066.hO1CYxl5Jz@milian-kdab2> <20161115011703.GL26543@kernel.org> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1853817.PuHzab5ZCC"; micalg="sha1"; protocol="application/pkcs7-signature" Return-path: Received: from mail.kdab.com ([176.9.126.58]:34342 "EHLO mail.kdab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750979AbcKPLRo (ORCPT ); Wed, 16 Nov 2016 06:17:44 -0500 In-Reply-To: <20161115011703.GL26543@kernel.org> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Arnaldo Carvalho de Melo Cc: linux-perf-users@vger.kernel.org --nextPart1853817.PuHzab5ZCC Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Monday, November 14, 2016 10:17:03 PM CET Arnaldo Carvalho de Melo wrote: > Em Mon, Nov 14, 2016 at 07:17:01PM +0100, Milian Wolff escreveu: > > On Monday, November 14, 2016 12:36:11 PM CET Arnaldo Carvalho de Melo wrote: > > > Em Mon, Nov 14, 2016 at 03:10:26PM +0100, Milian Wolff escreveu: > > > > features: > > > > > > > > - sample CPU events for a given application with backtraces > > > > > > > > perf record --call-graph dwarf ./foo > > > > > > > > - record switch-out events with backtraces (`-e > > > > sched:sched_switch/fp=dwarf/`) - somehow record the switch-in events, > > > > which are associated with a different process and thus currently > > > > discarded > > > > > > You want the backtraces with that, and since this is a meta-event... > > > Humm, > > > for the switch in would the above be sufficient? What value would be in > > > knowing the backtrace in that case? > > > > Knowing the backtrace would ensure I get the real location that triggered > > a > > switch, i.e. often times that comes from a syscall like futex or the like. > > Or > Sure, sure, a backtrace for a sched switch _out_ of a thread is useful, > and that you get from the sched:sched_switch tracepoint, what I'm > alluding to is the lack of a backtrace with the PERF_RECORD_SWITCH _IN_, > meta-event i.e. when the kernel switchs back to the thread being > monitored. I think my previous mail was confusing: Your approach works really well, thanks again. I do not need a backtrace for the switch-in in the general case. > > would I always get a CPU event (e.g. cycles) with a backtrace before the > > Is there a need for that? With sched:sched_switch + backtrace you get a > backtrace right at the moment of the sched_switch _out_, then, with > PERF_RECORD_SWITCH (--switch-events) you'll get the missing piece, the > sched switch _in_, that gets a CPU back to your thread. You'll not know > from where it came (the thread using the CPU right before this switch), > unless you're root, then PERF_RECORD_SWITCH _will_ have that info. Right, as said above - that is not too crucial. I simply need to know I'm getting switched in again, and at what time that happens. Thanks again! > > That gives me all information. With some post-processing one could then > > turn this into a really useful profiling tool, as one will only need a > > single perf record step to allow both, on-CPU as well as off-CPU > > profiling for application developers. > > right, off-cpu info in a 'perf trace' session is something we should > have, for instance. It should appear like a syscall, i.e. another way > out of the thread that will take some time to complete (sched_out ... > sched_in). Good idea, yes. -- 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 --nextPart1853817.PuHzab5ZCC 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 KUx9k5+9SryT7QMa44/P5W1QWtaXKZRagLBJetsulf24yr83OC0ePpFBrXBWx/BPP+gynnTKyJBU 6cZfD3idmkA8Dqxhql4Uj56HoWpQ3NeaTq8Fs6ZxlJxxs1BgCscTnTgHhgKo6ahpJhiQq0ywTyOr Ok+E2N/On+Fpb7vXQtdrROTHre5tQV9yWnEIN7N5ZaRZoJQ39wAvDcKSctrQOHLbFKhFxF0qfbe0 1sTurM0TRLfJK91DACX6YblpalgjEbenM49WdVn1zSnXRrcKK2W200JvFbK4e/vv6V1T1TRaJwID AQABo4HYMIHVMB8GA1UdIwQYMBaAFFMy0bPPf/rg8aBdhU6S0p5FHbRPMB0GA1UdDgQWBBStvZh6 NLQm9/rEJlTvA73gJMtUGjAOBgNVHQ8BAf8EBAMCAQYwDwYDVR0TAQH/BAUwAwEB/zARBglghkgB hvhCAQEEBAMCAQIwIAYDVR0lBBkwFwYKKwYBBAGCNwoDAwYJYIZIAYb4QgQBMD0GA1UdHwQ2MDQw MqAwoC6GLGh0dHA6Ly9jcmwudXNlcnRydXN0LmNvbS9VVE4tREFUQUNvcnBTR0MuY3JsMA0GCSqG SIb3DQEBBQUAA4IBAQDG7lMXaBSyUSIekFgNlP298XDlhi3DNjGPVEhG5y0IN7xsCmDhDq1RNOAS k+m+uKu4JrTplj0oj65kB/7gAezF45HrGKDxdX7bCuafkduvrnXfI5Fo3RcAWkv/ZGxw6wEa0JDZ x6bWbfYT5P+1ydIeKsuxJUMmeNkwm04NHr5p79/q/i2zzPmw3bUUypHUsrWl+wEZo0d5n52MlYc0 +B84kto2phH6a+tr6dxFeBU5BtdNQeQhyNwvh9G3v0hgdaViyyTeO2GgKSCmvsVsnMTpCmki75E6 +iav0VtBpzri+DgHQqvBW/jObboPBD8yNKzcBCjXcDAUJgbE5JuY1c94MIIEnTCCA4WgAwIBAgIQ ND3pK6wnNP+PyzSU+8xwVDANBgkqhkiG9w0BAQUFADBvMQswCQYDVQQGEwJTRTEUMBIGA1UEChML QWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVybmFsIFRUUCBOZXR3b3JrMSIwIAYD VQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290MB4XDTA1MDYwNzA4MDkxMFoXDTIwMDUzMDEw NDgzOFowga4xCzAJBgNVBAYTAlVTMQswCQYDVQQIEwJVVDEXMBUGA1UEBxMOU2FsdCBMYWtlIENp dHkxHjAcBgNVBAoTFVRoZSBVU0VSVFJVU1QgTmV0d29yazEhMB8GA1UECxMYaHR0cDovL3d3dy51 c2VydHJ1c3QuY29tMTYwNAYDVQQDEy1VVE4tVVNFUkZpcnN0LUNsaWVudCBBdXRoZW50aWNhdGlv biBhbmQgRW1haWwwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCyOYWk8n2rQTtiRjeu zcFgdbw5ZflKGkeiucxIzGqY1U01GbmkQuXOSeKKLx580jEHx060g2SdLinVomTEhb2FUTV5pE5o kHsceqSSqBfymBXyk8zJpDKVuwxPML2YoAuL5W4bokb6eLyib6tZXqUvz8rabaov66yhs2qqty5n NYt54R5piOLmRs2gpeq+C852OnoOm+r82idbPXMfIuZIYcZM82mxqC4bttQxICy8goqOpA6l14lD /BZarx1x1xFZ2rqHDa/68+HC8KTFZ4zW1lQ63gqkugN3s2XI/R7TdGKqGMpokx6hhX71R2XL+E1X KHTSNP8wtu72YjAUjCzrAgMBAAGjgfQwgfEwHwYDVR0jBBgwFoAUrb2YejS0Jvf6xCZU7wO94CTL VBowHQYDVR0OBBYEFImCZ33EnSZwAEu0UEh83j2uBG59MA4GA1UdDwEB/wQEAwIBBjAPBgNVHRMB Af8EBTADAQH/MBEGA1UdIAQKMAgwBgYEVR0gADBEBgNVHR8EPTA7MDmgN6A1hjNodHRwOi8vY3Js LnVzZXJ0cnVzdC5jb20vQWRkVHJ1c3RFeHRlcm5hbENBUm9vdC5jcmwwNQYIKwYBBQUHAQEEKTAn MCUGCCsGAQUFBzABhhlodHRwOi8vb2NzcC51c2VydHJ1c3QuY29tMA0GCSqGSIb3DQEBBQUAA4IB AQABvJzjYyiw8zEBwt973WKgAZ0jMQ+cknNTUeofTPrWn8TKL2d+eDMPdBa5kYeR9Yom+mRwANge +QsEYlCHk4HU2vUj2zS7hVa0cDRueIM3HoUcxREVkl+HF72sav3xwtHMiV+xfPA+UfI183zsYJhr Oivg79+zfYbrtRv1W+yifJgT1wBQudEtc94DeHThBYUxXsuauZ2UxrmUN3Vy3ET7Z+jw+iUeUqfa JelH4KDHPKBOsQo2+3dIn++Xivu0/uOUFKiDvFwtP9JgcWDuwnGCDOmINuPaILSjoGyqlku4gI51 ykkH9jsUut/cBdmf2+Cy5k2geCbn5y1uf1/GHogVMIIFGjCCBAKgAwIBAgIQbRnqpxlPajMi5iIy eqpx3jANBgkqhkiG9w0BAQUFADCBrjELMAkGA1UEBhMCVVMxCzAJBgNVBAgTAlVUMRcwFQYDVQQH Ew5TYWx0IExha2UgQ2l0eTEeMBwGA1UEChMVVGhlIFVTRVJUUlVTVCBOZXR3b3JrMSEwHwYDVQQL ExhodHRwOi8vd3d3LnVzZXJ0cnVzdC5jb20xNjA0BgNVBAMTLVVUTi1VU0VSRmlyc3QtQ2xpZW50 IEF1dGhlbnRpY2F0aW9uIGFuZCBFbWFpbDAeFw0xMTA0MjgwMDAwMDBaFw0yMDA1MzAxMDQ4Mzha MIGTMQswCQYDVQQGEwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdT YWxmb3JkMRowGAYDVQQKExFDT01PRE8gQ0EgTGltaXRlZDE5MDcGA1UEAxMwQ09NT0RPIENsaWVu dCBBdXRoZW50aWNhdGlvbiBhbmQgU2VjdXJlIEVtYWlsIENBMIIBIjANBgkqhkiG9w0BAQEFAAOC AQ8AMIIBCgKCAQEAkoSEW0tXmNReL4uk4UDIo1NYX2Zl8TJO958yfVXQeExVt0KU4PkncQfFxmmk uTLE8UAakMwnVmJ/F7Vxaa7lIBvky2NeYMqiQfZq4aP/uN8fSG1lQ4wqLitjOHffsReswtqCAtbU MmrUZ28gE49cNfrlVICv2HEKHTcKAlBTbJUdqRAUtJmVWRIx/wmi0kzcUtve4kABW0ho3cVKtODt JB86r3FfB+OsvxQ7sCVxaD30D9YXWEYVgTxoi4uDD216IVfmNLDbMn7jSuGlUnJkJpFOpZIP/+Cx YP0ab2hRmWONGoulzEKbm30iY9OpoPzOnpDfRBn0XFs1uhbzp5v/wQIDAQABo4IBSzCCAUcwHwYD VR0jBBgwFoAUiYJnfcSdJnAAS7RQSHzePa4Ebn0wHQYDVR0OBBYEFHoTTgB0W8Z4Y2QnwS/ioFu8 ecV7MA4GA1UdDwEB/wQEAwIBBjASBgNVHRMBAf8ECDAGAQH/AgEAMBEGA1UdIAQKMAgwBgYEVR0g ADBYBgNVHR8EUTBPME2gS6BJhkdodHRwOi8vY3JsLnVzZXJ0cnVzdC5jb20vVVROLVVTRVJGaXJz dC1DbGllbnRBdXRoZW50aWNhdGlvbmFuZEVtYWlsLmNybDB0BggrBgEFBQcBAQRoMGYwPQYIKwYB BQUHMAKGMWh0dHA6Ly9jcnQudXNlcnRydXN0LmNvbS9VVE5BZGRUcnVzdENsaWVudF9DQS5jcnQw JQYIKwYBBQUHMAGGGWh0dHA6Ly9vY3NwLnVzZXJ0cnVzdC5jb20wDQYJKoZIhvcNAQEFBQADggEB AIXWvnhXVW0zf0RS/kLVBqgBA4CK+w2y/Uq/9q9BSfUbWsXSrRtzbj7pJnzmTJjBMCjfy/tCPKEl Pgp11tA9OYZm0aGbtU2bb68obB2v5ep0WqjascDxdXovnrqTecr+4pEeVnSy+I3T4ENyG+2P/WA5 IEf7i686ZUg8mD2lJb+972DgSeUWyOs/Q4Pw4O4NwdPNM1+b0L1garM7/vrUyTo8H+2b/5tJM75C KTmD7jNpLoKdRU2oadqAGx490hpdfEeZpZsIbRKZhtZdVwcbpzC+S0lEuJB+ytF5OOu0M/qgOl0m WJ5hVRi0IdWZ1eBDQEIwvuql55TSsP7zdfl/bucwggZKMIIFMqADAgECAhByCOhbkTwXiJtaa0d5 K5u0MA0GCSqGSIb3DQEBBQUAMIGTMQswCQYDVQQGEwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5j aGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYDVQQKExFDT01PRE8gQ0EgTGltaXRlZDE5MDcG A1UEAxMwQ09NT0RPIENsaWVudCBBdXRoZW50aWNhdGlvbiBhbmQgU2VjdXJlIEVtYWlsIENBMB4X DTE0MDYwMjAwMDAwMFoXDTE3MDYwMTIzNTk1OVowggFZMQswCQYDVQQGEwJTRTEPMA0GA1UEERMG NjgzIDMxMRIwEAYDVQQIEwlWYWVybWxhbmQxEDAOBgNVBAcTB0hhZ2ZvcnMxGDAWBgNVBAkTD05v cnJpbmdzIHZhZWcgMjEPMA0GA1UEEhMGQm94IDMwMSYwJAYDVQQKDB1LbGFyw6RsdmRhbGVucyBE YXRha29uc3VsdCBBQjEdMBsGA1UECxMUQSBLREFCIEdyb3VwIENvbXBhbnkxQzBBBgNVBAsMOklz c3VlZCB0aHJvdWdoIEtsYXLDpGx2ZGFsZW5zIERhdGFrb25zdWx0IEFCIEUtUEtJIE1hbmFnZXIx HzAdBgNVBAsTFkNvcnBvcmF0ZSBTZWN1cmUgRW1haWwxFTATBgNVBAMTDE1pbGlhbiBXb2xmZjEk MCIGCSqGSIb3DQEJARYVbWlsaWFuLndvbGZmQGtkYWIuY29tMIIBIjANBgkqhkiG9w0BAQEFAAOC AQ8AMIIBCgKCAQEAwirYPAOcWQk9jaCoEAn84PwINg/NDs3PxsEd34f27AfCqJepwIF+ikMuBBxt mm1pieQwU9fcFrE4CXPCdYxfFOdcbJJ58Xzog5aFrJHnYGEFIL8KVvdBvAFeP/AJPaY2lg1JWnVI 1jwO74VmUGMyvMG286wpwW3hWO3sepZZQN3tvXyd9EgD72AiImkvw43+BW4xy8ptOd3TvEwCJ+uN x8v+uILsRLvKcmSrUsLpo7No2HoifWX1doKHKSwYVVqmOT/rjJWxF98j4w2kTKRsWdQ4ENlqNpjW zlbtB6TM2mrnInefzALbIoLLQ2E2NFCaMVsczf7RFsMxUepM9KQQ5QIDAQABo4IBzzCCAcswHwYD VR0jBBgwFoAUehNOAHRbxnhjZCfBL+KgW7x5xXswHQYDVR0OBBYEFGSjHixs9BD9OyGskYjMX7mi P+fiMA4GA1UdDwEB/wQEAwIFoDAMBgNVHRMBAf8EAjAAMB0GA1UdJQQWMBQGCCsGAQUFBwMEBggr BgEFBQcDAjBGBgNVHSAEPzA9MDsGDCsGAQQBsjEBAgEDBTArMCkGCCsGAQUFBwIBFh1odHRwczov L3NlY3VyZS5jb21vZG8ubmV0L0NQUzBXBgNVHR8EUDBOMEygSqBIhkZodHRwOi8vY3JsLmNvbW9k b2NhLmNvbS9DT01PRE9DbGllbnRBdXRoZW50aWNhdGlvbmFuZFNlY3VyZUVtYWlsQ0EuY3JsMIGI BggrBgEFBQcBAQR8MHowUgYIKwYBBQUHMAKGRmh0dHA6Ly9jcnQuY29tb2RvY2EuY29tL0NPTU9E T0NsaWVudEF1dGhlbnRpY2F0aW9uYW5kU2VjdXJlRW1haWxDQS5jcnQwJAYIKwYBBQUHMAGGGGh0 dHA6Ly9vY3NwLmNvbW9kb2NhLmNvbTAgBgNVHREEGTAXgRVtaWxpYW4ud29sZmZAa2RhYi5jb20w DQYJKoZIhvcNAQEFBQADggEBAFvi067uXCOkiUH/D6rv4gV0/e+e8DzcvbbsUxAC5nwDXBv+47ds l7j8NrZstZraVz35WEWgksNmnyghcuBKzKcN3kY1KNn/ERc9wvns/0dI+yj39L0eSMzchUZoV6GY MtPfmLofPvUBbDesl97JQXF9vpk8FIVsI1UKKrLzfoKhue5abQHXurSFa0ts1UPmSh2Y8/QCQlFN lCv8ISyEwVCAkhdIqxRc3hslooBhcRVUrYhRdCLlNN6Od8yuLE9sKWH/K4wg/BpnjCJmGp4GQhU8 DUG2r0CbOa+iZQKTWUgwdGU3Jr+WcOan/JaNzBuKk1GM3D+WcljoU7ZWtoqXPzgxggJaMIICVgIB ATCBqDCBkzELMAkGA1UEBhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UE BxMHU2FsZm9yZDEaMBgGA1UEChMRQ09NT0RPIENBIExpbWl0ZWQxOTA3BgNVBAMTMENPTU9ETyBD bGllbnQgQXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQQIQcgjoW5E8F4ibWmtHeSub tDAJBgUrDgMCGgUAoIGHMBgGCSqGSIb3DQEJAzELBgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8X DTE2MTExNjExMTc0MFowIwYJKoZIhvcNAQkEMRYEFG++QSl1QFUGRgZkIA8OzH7lDRQNMCgGCSqG SIb3DQEJDzEbMBkwCwYJYIZIAWUDBAECMAoGCCqGSIb3DQMHMA0GCSqGSIb3DQEBAQUABIIBAF/G 4nJ4BtBWDRbBGI9PBALbArzxutngIF/d2W8R392amDRnHurfmp3collij/4xITkKC7Ko/A8PJJcJ R3zMUVWK1cT5RHui2GV7clMT7p7zg3/pDZb2hUkmNPk2ED9tI/2BusYURPKYSYSl5aAESyI1Aabx D0cFv5yJn5O66e0/OejyWHcO1ro+WkkEZbkDWwed2cvayCdJUYP1TbOXcL1wt7Ux2hbi3aFPLdmr xNg+pPW4PqtPH4B+OhQj3Gd5tDcDRdA+bB4G/sZcIqW80URfyRa0XPgZwfI5xDyIyRqLaEa23qOj Wh8nOgxVUjO4Tx/USSklUpxbOu610OlZDpIAAAAAAAA= --nextPart1853817.PuHzab5ZCC--