---------- Forwarded message ---------- From: stephane eranian <eran...@googlemail.com> Date: Mon, Dec 15, 2008 at 1:58 PM Subject: Re: [patch] Performance Counters for Linux, v3 To: Paul Mackerras <pau...@samba.org> Cc: Ingo Molnar <mi...@elte.hu>, Peter Zijlstra <a.p.zijls...@chello.nl>, Vince Weaver <vi...@deater.net>, linux-ker...@vger.kernel.org, Thomas Gleixner <t...@linutronix.de>, Andrew Morton <a...@linux-foundation.org>, Eric Dumazet <da...@cosmosbay.com>, Robert Richter <robert.rich...@amd.com>, Arjan van de Veen <ar...@infradead.org>, Peter Anvin <h...@zytor.com>, "David S. Miller" <da...@davemloft.net>
Hi, On Mon, Dec 15, 2008 at 1:37 AM, Paul Mackerras <pau...@samba.org> wrote: > Ingo Molnar writes: > >> * stephane eranian <eran...@googlemail.com> wrote: >> >> > Hi, >> > >> > Given the level of abstractions you are using for the API, and given >> > your argument that the kernel can do the HW resource scheduling better >> > than anybody else. >> > >> > What happens in the following test case: >> > >> > - 2-way system (cpu0, cpu1) >> > >> > - on cpu0, two processes P1, P2, each self-monitoring and counting >> > event E1. >> > Event E1 can only be measured on counter C1. >> > >> > - on cpu1, there is a cpu-wide session, monitoring event E1, thus using >> > C1 >> > >> > - the scheduler decides to migrate P1 onto CPU1. You now have a >> > conflict on C1. >> > >> > How is this managed? >> >> If there's a single unit of sharable resource [such as an event counter, >> or a physical CPU], then there's just three main possibilities: either >> user 1 gets it all, or user 2 gets it all, or they share it. >> >> We've implemented the essence of these variants, with sharing the resource >> being the sane default, and with the sysadmin also having a configuration >> vector to reserve the resource to himself permanently. (There could be >> more variations of this.) >> >> What is your point? >> Could you explain what you mean by sharing here? Are you talking about time multiplexing the counter? ------------------------------------------------------------------------------ SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. The future of the web can't happen without you. Join us at MIX09 to help pave the way to the Next Web now. Learn more and register at http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
