linux-kernel - Re: [PATCH 4/7] perf, tool: Handle endianity swap on sample_id

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Date:	Mon, 21 May 2012 21:35:45 -0600
From:	David Ahern <dsahern@...il.com>
To:	Jiri Olsa <jolsa@...hat.com>
CC:	acme@...hat.com, a.p.zijlstra@...llo.nl, mingo@...e.hu,
	paulus@...ba.org, cjashfor@...ux.vnet.ibm.com, fweisbec@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/7] perf, tool: Handle endianity swap on sample_id_all
 header data

On 5/16/12 12:59 AM, Jiri Olsa wrote:
> Adding endianity swapping for event header attached via sample_id_all.
>
> Currently we dont do that and it's causing wrong data to be read when
> running report on architecture with different endianity than the record.
>
> Note, running following to test perf endianity handling:
> test 1)
>    - origin system:
>      # perf record -a -- sleep 10 (any perf record will do)
>      # perf report>  report.origin
>      # perf archive perf.data
>
>    - copy the perf.data, report.origin and perf.data.tar.bz2
>      to a target system and run:
>      # tar xjvf perf.data.tar.bz2 -C ~/.debug
>      # perf report>  report.target
>      # diff -u report.origin report.target
>
>    - the diff should produce no output
>      (besides some white space stuff and possibly different
>       date/TZ output)
>
> test 2)
>    - origin system:
>      # perf record -ag -fo /tmp/perf.data -- sleep 1
>    - mount origin system root to the target system on /mnt/origin
>    - target system:
>      # perf script --symfs /mnt/origin -I -i /mnt/origin/tmp/perf.data \
>       --kallsyms /mnt/origin/proc/kallsyms
>    - complete perf.data header is displayed
>
> Signed-off-by: Jiri Olsa<jolsa@...hat.com>

The code change is fine, but the commit message could use some 
additions: for example, what does the current output look like and how 
does the patch change it.

For example, perf is currently able to process 32-bit PPC samples on 
32-bit and 64-bit x86 -- that's the use case I have and it works. So an 
example of the affects of this patch for the commit log would be helpful.

Code wise:
Reviewed-by and Tested-by: David Ahern <dsahern@...il.com>
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