From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: "Liang, Kan" <kan.liang@intel.com>,
"mingo@kernel.org" <mingo@kernel.org>,
"acme@infradead.org" <acme@infradead.org>,
"eranian@google.com" <eranian@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V7 3/6] perf, x86: handle multiple records in PEBS buffer
Date: Wed, 6 May 2015 15:13:15 +0200 [thread overview]
Message-ID: <20150506131315.GA23123@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150506130116.GM2366@two.firstfloor.org>
On Wed, May 06, 2015 at 03:01:16PM +0200, Andi Kleen wrote:
> > > > + if (p->status != (1 << bit)) {
> > > > + u64 pebs_status;
> > > > +
> > > > + /* slow path */
> > > > + pebs_status = p->status & cpuc->pebs_enabled;
> > > > + pebs_status &= (1ULL << MAX_PEBS_EVENTS) - 1;
> > > > + if (pebs_status != (1 << bit)) {
> > > > + perf_log_lost(event);
> > >
> > > Does it make sense to keep an error[bit] count and only log once with the
> > > actual number in? -- when !0 obviously.
> >
> > Yes, will do it.
>
> If you use anything but u8 for the array member it would be too large
> for the NMI stack, and u8 is lilkely overflow prone. Would not do it.
If we're so close that 4*8=32 bytes would overflow the stack we're in
trouble already.
But we could just switch counts[] over to short and have another short
array for errors[], that way no extra bytes of stack used.
next prev parent reply other threads:[~2015-05-06 13:13 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-20 8:07 [PATCH V7 0/6] large PEBS interrupt threshold Kan Liang
2015-04-20 8:07 ` [PATCH V7 1/6] perf, x86: use the PEBS auto reload mechanism when possible Kan Liang
2015-04-20 8:07 ` [PATCH V7 2/6] perf, x86: introduce setup_pebs_sample_data() Kan Liang
2015-04-20 8:07 ` [PATCH V7 3/6] perf, x86: handle multiple records in PEBS buffer Kan Liang
2015-05-05 13:07 ` Peter Zijlstra
2015-05-05 13:17 ` Peter Zijlstra
2015-05-05 16:36 ` Liang, Kan
2015-05-05 17:00 ` Peter Zijlstra
2015-05-05 13:16 ` Peter Zijlstra
2015-05-05 16:30 ` Liang, Kan
2015-05-05 17:08 ` Peter Zijlstra
2015-05-05 17:22 ` Liang, Kan
2015-05-06 13:01 ` Andi Kleen
2015-05-06 13:13 ` Peter Zijlstra [this message]
2015-04-20 8:07 ` [PATCH V7 4/6] perf, x86: large PEBS interrupt threshold Kan Liang
2015-04-20 8:07 ` [PATCH V7 5/6] perf, x86: drain PEBS buffer during context switch Kan Liang
2015-04-20 8:07 ` [PATCH V7 6/6] perf, x86: enlarge PEBS buffer Kan Liang
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