From: Jason Baron <jbaron@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: hpa@zytor.com, rostedt@goodmis.org, mingo@elte.hu,
mathieu.desnoyers@polymtl.ca, tglx@linutronix.de,
andi@firstfloor.org, roland@redhat.com, rth@redhat.com,
masami.hiramatsu.pt@hitachi.com, fweisbec@gmail.com,
avi@redhat.com, davem@davemloft.net, sam@ravnborg.org,
ddaney@caviumnetworks.com, michael@ellerman.id.au,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH/RFC 1/2] jump label: make enable/disable o(1)
Date: Thu, 16 Dec 2010 14:36:35 -0500 [thread overview]
Message-ID: <20101216193635.GC2856@redhat.com> (raw)
In-Reply-To: <1292528031.2708.77.camel@laptop>
On Thu, Dec 16, 2010 at 08:33:51PM +0100, Peter Zijlstra wrote:
> On Thu, 2010-12-16 at 14:23 -0500, Jason Baron wrote:
> >
> > For the jump label disabled case, perf is using atomic_inc/dec and atomic_read
> > to check if enabled. While other consumers (tracepoints) are just using an
> > 'int'. I didn't want hurt the jump label disabled case for tracepoints.
> > If we can agree to use atomic ops for tracepoints, or drop atomics from
> > perf, that would simplify things.
>
> I had a quick look at the tracepoint stuff but got lost, but surely it
> has a reference count somewhere as well, it needs to know when the last
> probe goes away.. or does it check if the list is empty?
>
> Anyway, tracepoint enable/disable isn't a real fast-path, surely it
> could suffer an atomic op?
It is the atomic_read() at the tracepoint site that I am concerned
about.
thanks,
-Jason
next prev parent reply other threads:[~2010-12-16 19:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-16 18:25 [PATCH/RFC 0/2] jump label: simplify API Jason Baron
2010-12-16 18:25 ` [PATCH/RFC 1/2] jump label: make enable/disable o(1) Jason Baron
2010-12-16 19:10 ` Peter Zijlstra
2010-12-16 19:23 ` Jason Baron
2010-12-16 19:33 ` Peter Zijlstra
2010-12-16 19:36 ` Jason Baron [this message]
2010-12-16 19:41 ` Peter Zijlstra
2010-12-16 19:48 ` Jason Baron
2010-12-16 20:09 ` Steven Rostedt
2010-12-16 20:36 ` Mathieu Desnoyers
2010-12-16 20:43 ` Peter Zijlstra
2010-12-16 20:50 ` Mathieu Desnoyers
2010-12-16 20:56 ` Peter Zijlstra
2010-12-17 20:07 ` Jason Baron
2010-12-17 20:51 ` David Daney
2010-12-17 21:12 ` Steven Rostedt
2010-12-17 21:32 ` Jason Baron
2010-12-16 20:45 ` Mathieu Desnoyers
2010-12-16 18:25 ` [PATCH/RFC 2/2] jump label: introduce unlikely_switch() Jason Baron
2010-12-16 19:22 ` [PATCH/RFC 0/2] jump label: simplify API Mathieu Desnoyers
2010-12-16 20:18 ` Steven Rostedt
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