linux-kernel - Re: [PATCH v2 0/3] perf/sdt : Support for SDT markers

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Date:	Mon, 21 Jul 2014 17:54:43 +0530
From:	Hemant Kumar <hemant@...ux.vnet.ibm.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
CC:	linux-kernel@...r.kernel.org, srikar@...ux.vnet.ibm.com,
	peterz@...radead.org, oleg@...hat.com,
	hegdevasant@...ux.vnet.ibm.com, mingo@...hat.com, anton@...hat.com,
	systemtap@...rceware.org, namhyung@...nel.org,
	aravinda@...ux.vnet.ibm.com, penberg@....fi
Subject: Re: [PATCH v2 0/3] perf/sdt : Support for SDT markers


On 07/20/2014 08:46 AM, Masami Hiramatsu wrote:
> (2014/07/20 2:32), Hemant Kumar wrote:
>>>> [SNIP] 	
>>>> First, scan the binaries using :
>>>> # perf list sdt --scan
>>> At a glance, maybe we'd better have perf sdt-cache as like as perf buildid-cache
>>> for manage sdt information. what would you think?
>>>
>> I agree with you having perf sdt-cache similar to perf buildid-cache.
>> But I think if the functionality of perf sdt-cache is only to build the
>> cache, then we can
>> go with the perf list sdt --scan. Since, "perf list sdt" is used for
>> other purposes too, it
>> should be less confusing for the users to just add another option
>> (--scan) to create/modify
>> the cache. What do you suggest?
> I think there may be some other cases, for example adding user local build
> binary to the cache, or remove/update it locally. :)
>
> And also, in user's mental model of perf-list, it doesn't take an "active"
> action, that always does "passive" action. So adding such "active" scan option
> will be more confusing.

Ok, I understand now.

> But I also think it is OK that if the sdt is never scanned, the perf-list
> automatically scans in background (without any option) or suggests user
> to run "perf sdt-cache --scan". (it depends on how long time it may take)
>
> To summarize it, I'd like to suggest adding below functions;
>
> perf list sdt : shows all cached SDT events
> perf list sdt <file> : shows SDT events in <file>
> perf sdt-cache --scan/-s : scans all system binaries/libraries + added files
> perf sdt-cache --add/-a <file(s)> : add SDT events in <file> to cache
> perf sdt-cache --remove/-r <file(s)>: remove SDT events in <file> from cache

Yeah, I agree with the above mentioned functions.

So, according to this, if perf list sdt <file> can't find the SDT events 
for that file
in the SDT cache, should it say "use perf sdt-cache --add <file> to add 
the SDT
events for that file to the cache", or silently, should add that file's 
SDT events
to SDT cache?

> And if perf list can't find sdt-cache, it would suggest to run
> perf sdt-cache --scan or run it silently. :)
>
> [...]

-- 
Thanks,
Hemant Kumar

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