From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel@vger.kernel.org, bp@alien8.de,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 1/2] perf: Add munmap callback
Date: Thu, 25 Oct 2018 02:31:30 +0200 [thread overview]
Message-ID: <20181025003130.GU3109@worktop.c.hoisthospitality.com> (raw)
In-Reply-To: <20181024182854.GH6218@tassilo.jf.intel.com>
On Wed, Oct 24, 2018 at 11:28:54AM -0700, Andi Kleen wrote:
> > > void perf_event_mmap(struct vm_area_struct *vma)
> > > {
> > > struct perf_mmap_event mmap_event;
> > >
> > > if (!atomic_read(&nr_mmap_events))
> > > return;
> > > <SNIP>
> > > }
> > >
> >
> > Thanks. I'll add the nr_mmap_events check in V2.
>
> No, that's the wrong check here. The PEBS flush is independent of mmap
> events being requested.
>
> If anything would need to check for any PEBS events active, which
> would need a new counter. I think the easiest is to just check if
> this_cpu_ptr(&sched_cb_list)
> is empty, which should be good enough.
It is just the CLI+STI, not PUSHF;CLI+POPF that are required and that is
a lot cheaper already. Also, you need to have preemption disabled in
order to check the per-cpu cb list.
So I don't think it really makes much sense to try and frob a fast path
in there.
next prev parent reply other threads:[~2018-10-25 0:31 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-24 15:11 [PATCH 1/2] perf: Add munmap callback kan.liang
2018-10-24 15:11 ` [PATCH 2/2] perf/x86/intel: Fix missing physical address in large PEBS kan.liang
2018-10-24 16:23 ` [PATCH 1/2] perf: Add munmap callback Andi Kleen
2018-10-24 16:32 ` Arnaldo Carvalho de Melo
2018-10-24 18:12 ` Liang, Kan
2018-10-24 18:28 ` Andi Kleen
2018-10-25 0:31 ` Peter Zijlstra [this message]
2018-10-24 19:15 ` Arnaldo Carvalho de Melo
2018-10-24 19:30 ` Stephane Eranian
2018-10-25 0:23 ` Peter Zijlstra
2018-10-25 0:25 ` Stephane Eranian
2018-10-25 0:34 ` Peter Zijlstra
2018-10-25 0:44 ` Stephane Eranian
2018-11-01 14:09 ` Liang, Kan
2018-11-05 10:59 ` Stephane Eranian
2018-11-05 15:43 ` Liang, Kan
2018-11-06 15:00 ` Stephane Eranian
2018-11-06 16:47 ` Liang, Kan
2018-10-25 0:29 ` Peter Zijlstra
2018-10-25 14:00 ` Liang, Kan
2018-10-30 12:51 ` Peter Zijlstra
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