Date: Wed, 16 Jan 2008 22:39:09 -0500 (EST)
From: Steven Rostedt <rostedt@goodmis.org>
To: Paul Mackerras <paulus@samba.org>
cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>,
       john stultz <johnstul@us.ibm.com>, LKML <linux-kernel@vger.kernel.org>,
       Ingo Molnar <mingo@elte.hu>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Christoph Hellwig <hch@infradead.org>,
       Gregory Haskins <ghaskins@novell.com>,
       Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
       Thomas Gleixner <tglx@linutronix.de>, Tim Bird <tim.bird@am.sony.com>,
       Sam Ravnborg <sam@ravnborg.org>, "Frank Ch. Eigler" <fche@redhat.com>,
       Steven Rostedt <srostedt@redhat.com>,
       Daniel Walker <dwalker@mvista.com>
Subject: Re: [RFC PATCH 16/22 -v2] add get_monotonic_cycles
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On Thu, 17 Jan 2008, Paul Mackerras wrote:
>
> It's very hard to do a per-thread counter in the VDSO, since threads
> in the same process see the same memory, by definition.  You'd have to
> have an array of counters and have some way for each thread to know
> which entry to read.  Also you'd have to find space for tens or
> hundreds of thousands of counters, since there can be that many
> threads in a process sometimes.

I was thinking about this. What would also work is just the ability to
read the schedule counter for the current cpu. Now this would require that
the task had a way to know which CPU it was currently on.

-- Steve

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