linux-kernel - Re: [PATCH V2 0/2] ftrace: Introduce the new I/F "nr_saved

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Message-ID: <5382EB36.2060501@hitachi.com>
Date:	Mon, 26 May 2014 16:20:22 +0900
From:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Namhyung Kim <namhyung@...nel.org>, linux-kernel@...r.kernel.org,
	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Ingo Molnar <mingo@...hat.com>, yrl.pp-manager.tt@...achi.com
Subject: Re: [PATCH V2 0/2] ftrace: Introduce the new I/F "nr_saved_cmdlines"

Hi Steven,

Would you review this patch set?

Thanks,
Yoshihiro YUNOMAE

(2014/02/20 17:44), Yoshihiro YUNOMAE wrote:
> Hi,
>
> This patch set introduces the new I/F "nr_saved_cmdlines" for increasing
> the number of saved cmdlines. Current saved_cmdlines can store just 128 command
> names and PIDs, but process names are often lost like <...> when we read trace
> data. If the process exists, we can get the name by using ps command. However,
> if the process already has not existed, we cannot get the name.
>
> To solve this issue, we introduce the new I/F "nr_saved_cmdlines" to expand
> the max number of saved command line names. This I/F is very simple.
> If we write a number to nr_saved_cmdlines, the number of command name will be
> stored. And, if we read the I/F, we can get current maximum number of command
> name. The default number is 128 which is current default number, so this patch
> does not change the usage of memory for saved_cmdlines when we boot kernel.
>
> Thanks!
>
> Changes in V2:
> - Fix a racing problem of savedcmd between saved_cmdlines I/F and
>    nr_saved_cmdlines I/F. If one reads saved_cmdlines and writes a value to
>    nr_saved_cmdlines at the same time, then the write returns -EBUSY. [2/2]
>
> ---
>
> Yoshihiro YUNOMAE (2):
>        ftrace: Make saved_cmdlines use seq_read
>        ftrace: Introduce nr_saved_cmdlines I/F
>
>
>   kernel/trace/trace.c |  316 +++++++++++++++++++++++++++++++++++++++++---------
>   1 file changed, 261 insertions(+), 55 deletions(-)
>

-- 
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@...achi.com


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