linux-kernel - Re: how to use perf annotate on the kernel

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Message-ID: <20100603180613.GA10469@ghostprotocols.net>
Date:	Thu, 3 Jun 2010 15:06:13 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	paulus@...ba.org, davem@...emloft.net, fweisbec@...il.com,
	perfmon2-devel@...ts.sf.net, eranian@...il.com, tzanussi@...il.com
Subject: Re: how to use perf annotate on the kernel

Em Thu, Jun 03, 2010 at 02:54:45PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Jun 03, 2010 at 07:23:02PM +0200, Stephane Eranian escreveu:
> > # perf annotate (or annotate -d '[kernel.kallsyms]'?)
> > Can't annotate __lock_acquire: No vmlinux file was found in the path
> > 
> > # perf annotate -k vmlinux
> > objdump: '[kernel.kallsyms]': No such file
> 
> This looks like a bug in how it reports this problem, probably vmlinux
> is not in the current directory, or it is but has a build-id that
> doesn't matches the one in the perf.data file.
> 
> But the message is wrong, should be like it is in the tui, for this same
> situation:
> 
> 	ui_helpline__puts("No vmlinux file found, can't "
> 			  "annotate with just a kallsyms file");
> 
> > Am I missing something here?
> 
> If you don't specify it with --vmlinux/-k it will try to find it in one
> of these places:
> 
>         vmlinux_path[vmlinux_path__nr_entries] = strdup("vmlinux");
>         vmlinux_path[vmlinux_path__nr_entries] = strdup("/boot/vmlinux");
>         snprintf(bf, sizeof(bf), "/boot/vmlinux-%s", uts.release);
>         vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
>         snprintf(bf, sizeof(bf), "/lib/modules/%s/build/vmlinux", uts.release);
>         vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
>         snprintf(bf, sizeof(bf), "/usr/lib/debug/lib/modules/%s/vmlinux",
>                  uts.release);
>         vmlinux_path[vmlinux_path__nr_entries] = strdup(bf);
> 
> It also now looks at /sys/kernel/notes, gets the build-id, and looks up
> in the build-id cache.

For instance, here using -vvv I get:

[root@...lia ~]# perf annotate -vvv memcpy > /dev/null
build id event received for [kernel.kallsyms]: 310920b54cbbf242dbfa09052f652806d2c73821
build id event received for /lib64/libtinfo.so.5.7: cd9da7b5b1fcb25ee6b3762bb9fe62f782590fd5
Looking at the vmlinux_path (6 entries long)
No build_id in /root/.debug/.build-id/31/0920b54cbbf242dbfa09052f652806d2c73821, ignoring it
No build_id in vmlinux, ignoring it
No build_id in /boot/vmlinux, ignoring it
No build_id in /boot/vmlinux-2.6.35-rc1, ignoring it
Using /lib/modules/2.6.35-rc1/build/vmlinux for symbols
hist_entry__inc_addr_samples: ip=0xffffffff811ea69e
0xffffffff811ea690 memcpy: period++ [ip: 0xffffffff811ea69e, 0xe] => 1
hist_entry__annotate: filename=/lib/modules/2.6.35-rc1/build/vmlinux, sym=memcpy, start=0xffffffff811ea690, end=0xffffffff811ea730
annotating [0x187e770] /lib/modules/2.6.35-rc1/build/vmlinux : [0x19b1f70]                         memcpy
Executing: objdump --start-address=0xffffffff811ea690 --stop-address=0xffffffff811ea730 -dS /lib/modules/2.6.35-rc1/build/vmlinux|grep -v /lib/modules/2.6.35-rc1/build/vmlinux|expand
[root@...lia ~]# 

I'm removing all vmlinux from the path so that I can reproduce what you see.

- Arnaldo
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