linux-kernel - Re: [RFC 0/5] perf: Allow leader sampling on inherited events

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Date:	Sat, 23 Aug 2014 22:07:59 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	"Jen-Cheng(Tommy) Huang" <tommy24@...ech.edu>
Cc:	Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/5] perf: Allow leader sampling on inherited events

On Sat, Aug 23, 2014 at 02:55:32PM -0400, Jen-Cheng(Tommy) Huang wrote:
> Hi Jiri,
> 
> 1. Thank you so much for providing the patch.
> I am trying to test out the patch.
> (I got the source using "git checkout -b perf
> remotes/origin/perf/core_format_group"
> after clone)
> However, the perf in your repo seems having issues with sample_read :S.
> (:S works fine with my original perf that comes with the kernel.)
> When I do
> perf record -e '{instructions,cycles}:S' /bin/ls
> 
> The following error is shown
> Error:
> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for
> event (instructions).
> /bin/dmesg may provide additional information.
> No CONFIG_PERF_EVENTS=y kernel support configured?
> 
> This error does not occur without :S.
> perf record -e '{instructions,cycles}' /bin/ls
> This shows no errors.

have u boot the new kernel? there're 2 kernel patches
within the patchset

but right, the perf code should detect the kernel change
and keep old behaviour if it's not detected..

> 
> 2. Another issue I have is to show the sample value using 'perf script'.
> Currently, I am using perf report -D to show the sample read values, the
> format is not what I need. Could you give me some hints on where to modify
> to show the sample values using perf script?

there's no support in perf script to display the sample
read values.. I'll check if that could be added

thanks,
jirka
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