linux-kernel - Re: [PATCH v2 5/5] perf: make perf buildid-list work better with pipe mode

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Date:	Tue, 15 May 2012 21:55:36 -0600
From:	David Ahern <dsahern@...il.com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	acme@...hat.com
Subject: Re: [PATCH v2 5/5] perf: make perf buildid-list work better with
 pipe mode

On 5/15/12 5:28 AM, Stephane Eranian wrote:
> In order for perf buildid-list to work with pipe-mode files,
> it needs to process buildids and event attr structs.
>
> $ perf record -o - noploop 2 | ./perf inject -b | perf buildid-list -i - -H
> noploop for 2 seconds
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.084 MB - (~3678 samples) ]
> 0000000000000000000000000000000000000000 [kernel.kallsyms]
> 3a0d0629efe74a8da3eeba372cdbd74ad9b8f5d5 /usr/local/bin/noploop
>
> The reason [kernel.kallsyms] shows a 0 build-id comes from the
> way buildids are injected in the stream. The buildid for the kernel
> is provided by a BUILD_ID record. The [kernel.kallsyms] is provided
> by a MMAP record. There is no clean and obvious way to link the two,
> unfortunately. In regular mode, the kernel buildid is generated from
> reading the ELF image or kallsyms and perf knows to associate
> [kernel.kallsyms] to it. Later on, when perf processes the
> [kernel.kallsyms] MMAP record, it will already have a dso for it.
>
> So for now, make sure perf buildid-list shows the buildids for
> everything but the kernel image.
>
> Signed-off-by: Stephane Eranian<eranian@...gle.com>
> ---
>   tools/perf/builtin-buildid-list.c |    6 +++++-
>   tools/perf/util/build-id.c        |    2 ++
>   2 files changed, 7 insertions(+), 1 deletions(-)

Reviewed-and-tested-by: David Ahern <dsahern@...il.com>
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