linux-kernel - Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:

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Date:	Wed, 30 Oct 2013 19:22:38 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Pekka Enberg <penberg@....fi>
Cc:	David Ahern <dsahern@...il.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Hemant Kumar <hkshaw@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"hegdevasant@...ux.vnet.ibm.com" <hegdevasant@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...hat.com>,
	"anton@...hat.com" <anton@...hat.com>,
	"systemtap@...rceware.org" <systemtap@...rceware.org>,
	Namhyung Kim <namhyung@...nel.org>,
	"aravinda@...ux.vnet.ibm.com" <aravinda@...ux.vnet.ibm.com>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:

(2013/10/29 3:45), Pekka Enberg wrote:
> On 10/28/13 6:59 PM, David Ahern wrote:
>  > I often use perf-list to lookup an exact event name, and I do not want
>  > to see it taking many seconds to minutes to run (not everyone is
>  > running on an SSD). I also run perf on many different OS versions with
>  > an NFS home directory, and do not want to see a cache explosion (I
>  > have buildid disabled for this reason).
> 
> I am talking about reasonable defaults - the 'default' part implies that
> people can change the behavior.  So we absolutely should also have
> something like this for power users such as yourself:
> 
>    perf config sdt.scan false

Ah, I like this perf-config to store the default/customized values ;)

> That said, the 'reasonable' part suggests that 'perf list' must not take
> seconds or minutes (!) for every run.  I'd start with implementing a
> naive scan and seeing where it takes us.  It's not like it's rocket
> science to ignore network mounts or revert to a whitelist of paths if
> necessary.

I think it is reasonable to scan only $PATH and ld.so.cache (the result
of ldconfig --print-cache) by default. :)

Thank you,



-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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