From: Peter Zijlstra <peterz@infradead.org>
To: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org, Mike Galbraith <efault@gmx.de>,
Arjan van de Ven <arjan@infradead.org>,
Wu Fengguang <fengguang.wu@intel.com>,
Eric Dumazet <dada1@cosmosbay.com>
Subject: Re: [PATCH 1/9] perf_counter: unify and fix delayed counter wakeup
Date: Sun, 29 Mar 2009 11:25:10 +0200 [thread overview]
Message-ID: <1238318710.23852.38.camel@twins> (raw)
In-Reply-To: <1238318201.23852.17.camel@twins>
On Sun, 2009-03-29 at 11:16 +0200, Peter Zijlstra wrote:
> On Sun, 2009-03-29 at 11:14 +1100, Paul Mackerras wrote:
> > Peter Zijlstra writes:
> >
> > > While going over the wakeup code I noticed delayed wakeups only work
> > > for hardware counters but basically all software counters rely on
> > > them.
> >
> > Hmmm, I don't like the extra latency this introduces, particularly
> > since on powerpc we already have a good way to avoid the latency.
>
> Right, so I can re-instate the powerpc bits and have it call
> perf_counter_do_pending() whenever it finds the per-cpu pending bit set.
>
> I'd have to look into the fancy new per-cpu stuff for the x86 bits, but
> I'm reasonably sure something like that should be doable.
In a perfect world, I'd introduce a self-ipi on UP and use that. Also,
in that same perfect world, all arches would support cmpxchg()/xchg() so
we could put the whole thing in generic code.
next prev parent reply other threads:[~2009-03-29 9:25 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-28 19:43 [PATCH 0/9] perf_counter patches Peter Zijlstra
2009-03-28 19:44 ` [PATCH 1/9] perf_counter: unify and fix delayed counter wakeup Peter Zijlstra
2009-03-29 0:14 ` Paul Mackerras
2009-03-29 9:16 ` Peter Zijlstra
2009-03-29 9:25 ` Peter Zijlstra [this message]
2009-03-29 10:02 ` Paul Mackerras
2009-03-28 19:44 ` [PATCH 2/9] perf_counter: fix update_userpage() Peter Zijlstra
2009-03-29 0:24 ` Paul Mackerras
2009-04-02 8:50 ` Peter Zijlstra
2009-04-02 9:00 ` Peter Zijlstra
2009-04-02 9:21 ` Paul Mackerras
2009-04-02 9:28 ` Peter Zijlstra
2009-04-02 9:15 ` Paul Mackerras
2009-04-02 9:36 ` Peter Zijlstra
2009-04-02 9:58 ` Paul Mackerras
2009-04-02 10:36 ` Peter Zijlstra
2009-03-28 19:44 ` [PATCH 3/9] perf_counter: kerneltop: simplify data_head read Peter Zijlstra
2009-03-28 19:44 ` [PATCH 4/9] perf_counter: executable mmap() information Peter Zijlstra
2009-03-28 19:44 ` [PATCH 5/9] perf_counter: kerneltop: parse the mmap data stream Peter Zijlstra
2009-03-28 19:44 ` [PATCH 6/9] perf_counter: powerpc: only reserve PMU hardware when we need it Peter Zijlstra
2009-03-28 19:44 ` [PATCH 7/9] perf_counter: make it possible for hw_perf_counter_init to return error codes Peter Zijlstra
2009-03-30 4:13 ` Paul Mackerras
2009-03-28 19:44 ` [PATCH 8/9] perf_counter tools: optionally scale counter values in perfstat mode Peter Zijlstra
2009-03-28 19:44 ` [PATCH 9/9] RFC perf_counter: event overlow handling Peter Zijlstra
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