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Date:	Tue, 10 Nov 2009 12:16:49 -0800
From:	john stultz <johnstul@...ibm.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Sean Foley <Sean_Foley@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Darren Hart <dvhltc@...ibm.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Mike Fulton <fultonm@...ibm.com>
Subject: Re: [RFC][PATCH] Add prctl to set sibling thread names

On Tue, 2009-11-10 at 14:27 +0900, KOSAKI Motohiro wrote:
> Hi Sean, John,
> 
> > Kosaki,
> > Here are a couple of use cases previously posted to this thread on the linux kernel mailing list:
> > 
> > dispatch thread adds context to thread names:
> > http://marc.info/?l=linux-kernel&m=125660141231348&w=2
> > 
> > java language support:
> > http://marc.info/?l=linux-kernel&m=125666430720863&w=2
> > 
> > 
> > 
> > Here are some various specific use cases from the web:
> > 
> > Attaching additional info to thread names when used for different purposes:
> > http://osdir.com/ml/java.jsr.166-concurrency/2006-12/msg00105.html
> > 
> > Threads obtained from thread pools being reassigned new names:
> > http://haacked.com/archive/2004/06/07/546.aspx
> > http://bytes.com/topic/c-sharp/answers/637152-naming-backgroundworker-thread
> > 
> > Renaming threads scattered across third-party libraries by enumerating them and renaming them dynamically:
> > http://stackoverflow.com/questions/467224/renaming-threads-in-java
> 
> Okey, good explanation. thanks!
> 
> So, I would suggested to extend /proc/{pid}/cmdline instead using task->comm.
> because 
>   - task->comm has nasty locking rule. It is harder to change SMP safe.

I cc'ed you on the updated patch which addresses this. Please let me
know if you have specific concerns there.

>   - ps (and other procps tools) already support /proc/{pid}/cmdline.
>   - task->comm is restrected 16 character length, /proc/cmdline isn't.

Part of the reason to use comm is that most tools like perf or oprofile,
use comm, instead of cmd. Additionally, looking at cmdline, that's per
mm not per task, right? So it wouldn't really work for thread names. 

Please correct me if I'm not seeing what you're really suggesting.

thanks
-john


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