From: Milian Wolff <milian.wolff@kdab.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Steinar H. Gunderson" <sgunderson@bigfoot.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>
Subject: Re: Inlined functions in perf report
Date: Tue, 20 Dec 2016 14:27:10 +0100
Message-ID: <2027151.EnbG4A8ymx@milian-kdab2>
Organization: KDAB
In-Reply-To: <20161220121755.GL3124@twins.programming.kicks-ass.net>
References: <20161220115954.GA35897@sesse.net> <20161220121755.GL3124@twins.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="nextPart8619909.WDQz9TpWy4"; micalg="sha1"; protocol="application/pkcs7-signature"
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 13057
Lines: 255

--nextPart8619909.WDQz9TpWy4
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset="UTF-8"

On Tuesday, December 20, 2016 1:17:55 PM CET Peter Zijlstra wrote:
> On Tue, Dec 20, 2016 at 12:59:54PM +0100, Steinar H. Gunderson wrote:
> > Hi Peter,
> >=20
> > I can't find a good point of contact for perf, so I'm contacting you ba=
sed
> > on the MAINTAINERS file; feel free to redirect somewhere if you're not
> > the right person.
>=20
> Cc'ed linux-perf-users@vger.kernel.org
>=20
> > I'm trying to figure out how to deal with perf report when there are
> > inlined functions; they don't generally seem to show up in the call
> > stack, which sometimes can make it very hard to figure out what is goin=
g,
> > especially in a code base one doesn't know too well. As an example, I
> > threw together a>=20
> > minimal test program:
> >   #include <stdlib.h>
> >  =20
> >   inline int foo()
> >   {
> >  =20
> >           int k =3D rand();
> >           int sum =3D 1;
> >           for (int i =3D 0; i < 10000000000; ++i)
> >           {
> >          =20
> >                   sum ^=3D k;
> >                   sum +=3D k;
> >          =20
> >           }
> >           return sum;
> >  =20
> >   }
> >  =20
> >   int main(void)
> >   {
> >  =20
> >           return foo();
> >  =20
> >   }
> >=20
> > Compiling with -O2 -g, and running perf record -g yields:
> >   # Samples: 6K of event 'cycles:ppp'
> >   # Event count (approx.): 5876825543
> >   #
> >   # Children      Self  Command  Shared Object      Symbol
> >   # ........  ........  .......  .................  ...................=
=2E..
> >   #
> >  =20
> >       99.98%    99.98%  inline   inline             [.] main
> >      =20
> >               ---0x706258d4c544155
> >              =20
> >                  main
> >      =20
> >       99.98%     0.00%  inline   [unknown]          [.] 0x0706258d4c544=
155
> >      =20
> >               ---0x706258d4c544155
> >              =20
> >                  main
> >=20
> > Is there a way I can get it to show =E2=80=9Cfoo=E2=80=9D in the call g=
raph? (I suppose
> > also ideally, =E2=80=9Cfoo=E2=80=9D and not =E2=80=9Cmain=E2=80=9D shou=
ld show up in a non-graph run.) Of
> > course, this gets even more confusing if foo calls bar, since it now
> > looks like the call chain is main -> bar directly.
> >=20
> > I have debug information that should be sufficient in the binary, becau=
se
> > if>=20
> > I break in gdb, I definitely get the call stack:
> >   Program received signal SIGINT, Interrupt.
> >   0x0000555555554589 in foo () at inline.c:5
> >   5               int k =3D rand();
> >   (gdb) bt
> >   #0  0x0000555555554589 in foo () at inline.c:5
> >   #1  main () at inline.c:17
> >   (gdb)
> >=20
> > FWIW, this is with perf from 4.10 (git as of a few days ago) and GCC
> > 6.2.1.
>=20
> OK, so it might be possible with: perf record -g --call-graph dwarf
> but that's fairly heavy on the overhead, it will dump the top-of-stack
> for each sample (8k default) and unwind using libunwind in userspace.

It is not even possible with that, perf report is lacking the steps require=
d=20
to add inline frames - it will only add "real" frames it gets from either o=
f=20
the unwind libraries.

I have a WIP patch available for this functionality though, it can be found=
=20
here (depends on libbfd, i.e. bfd_find_inliner_info):

https://github.com/milianw/linux/commit/
71d031c9d679bfb4a4044226e8903dd80ea601b3

This is not yet upstreamable, but any early comments would be welcome. I ho=
pe=20
to get some more time to drive this in the coming weeks. If you want to tes=
t=20
it out, checkout my milian/perf branch of this repo, build it like you'd do=
=20
the normal user-space perf, then run

perf report -g srcline -s sym,srcline

> The default mechanism used for call-graphs is frame-pointers which are
> (relatively) simple and fast to traverse from kernel space. The down
> side is of course that all your userspace needs to be compiled with
> frame pointers enabled and inlined functions, as you noticed, are
> 'lost'.
>=20
> There has been talk to attempt to utilize the ELF EH frames which are
> mandatory in the x86_64 ABI (even for C) to attempt a kernel based
> 'DWARF' unwind, but nobody has put forward working code for this yet.
> Also, even if the EH stuff is mapped at runtime, it doesn't mean the
> pages will actually be loaded (due to demand paging) and available for
> use, which also will limit usability. (perf sampling is using
> interrupt/NMI context and we cannot page from that, so we're limited to
> memory that's present.)

While all of this would be nice to have, it is not directly related to=20
inlining from what I gathered.

Bye

=2D-=20
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
--nextPart8619909.WDQz9TpWy4
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
DTE2MTIyMDEzMjcxMFowIwYJKoZIhvcNAQkEMRYEFAa3C3wHh6D46LHswlkfar62InkIMCgGCSqG
SIb3DQEJDzEbMBkwCwYJYIZIAWUDBAECMAoGCCqGSIb3DQMHMA0GCSqGSIb3DQEBAQUABIIBAGjb
Z30+LMNUq6pSKiYF4yeAvPrTLUzamCotd89CdV92IMjblBDk1CEl25z6t8DPN+zM7GJuG30i3x7F
U9gdBt49UtsTuPKasNYkgBTzg+BN9QUeYbMTujm7uKFHkMu50OAeYwS39RFtjmOXXReNrqzOPKPb
i+W52qG+IrqrZx0HZbx5JK5W+ROnbeab7IPh5rrXqdLVjnTwG5jahrWACHu4QFO0QqNq2dRnomlJ
bPupuJENQxr8ceBPbEmwpmbID3c/Tv9XbqVJ7M63tCIeodSb9kis4ULTq8plWP3hOSjtkP4ATMD3
D1i3e8sBeTnlhMsNXqji0qN4E6sCy6J6N6AAAAAAAAA=


--nextPart8619909.WDQz9TpWy4--