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

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Message-ID: <5270D9F7.3090105@hitachi.com>
Date:	Wed, 30 Oct 2013 19:05:43 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Hemant Kumar <hkshaw@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Oleg Nesterov <oleg@...hat.com>,
	hegdevasant@...ux.vnet.ibm.com, Ingo Molnar <mingo@...hat.com>,
	anton@...hat.com, systemtap@...rceware.org,
	Namhyung Kim <namhyung@...nel.org>,
	aravinda@...ux.vnet.ibm.com, dsahern@...il.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:

(2013/10/26 20:16), Frank Ch. Eigler wrote:
> Pekka Enberg <penberg@...nel.org> writes:
> 
>> Is there a technical reason why 'perf list' could not show all the
>> available SDT markers on a system and that the 'mark to event'
>> mapping cannot happen automatically? [...]
> 
> A quick experiment with:
> 
>   find `echo $PATH | tr : ' '` -type f -perm -555 | 
>        xargs readelf -n 2>/dev/null | 
>        grep STAP 2>/dev/null 
> 
> suggests reasonable performance for my F19 workstation (a second or
> two over ~6000 executables), once all the ELF content is in the block
> cache.  According to a stap eventcount.stp run, that required about
> 50000 syscall.read events.
> 
> Note that a $PATH search excludes shared libraries, which can also
> carry <sys/sdt.h> markers.  Adding /usr/lib* in more than doubles the
> work, then there's /usr/libexec etc.

To find all system libraries, we can use ldconfig.

$ ldconfig --print-cache

shows what dynamic libraries will be loaded. On my own laptop (running
ubuntu13.04) shows ~1000 libs.

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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