linux-kernel - Re: [announce] Performance Counters for Linux, v6

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Date:	Fri, 20 Feb 2009 15:04:41 -0800
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephane Eranian <eranian@...glemail.com>,
	Eric Dumazet <dada1@...mosbay.com>,
	Robert Richter <robert.richter@....com>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Anvin <hpa@...or.com>, Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	Mike Galbraith <efault@....de>
Subject: Re: [announce] Performance Counters for Linux, v6



Peter Zijlstra wrote:
> On Fri, 2009-02-20 at 14:38 -0800, Corey Ashford wrote:
>> There may be other non-event-related changes that will not be handled 
>> quite as well in this way.  In the original email I hinted at that we 
>> may want an option for mmap'd sample buffers at some point, and so I'm 
>> not clear how you'd provide an ABI to request mmap'd buffers (you would 
>> probably need to be able to request the size and get back a pointer to 
>> the mmap'd buffer).  Would this be done through a special 
>> sys_perf_counter_open call?  Or through a subsequent ioctl call on the 
>> group leader after an open (which requires the counters to be initially 
>> disabled), etc.
> 
> What's stopping a regular mmap() call using the fd obtained from
> sys_perf_counter_open() ?

Perhaps nothing.  I don't know why it didn't occur to me that this could 
be done.  If PCL supports this, great!

Thanks for your reply!

-- 
Regards,

- Corey

Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjashfor@...ibm.com

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