From: Peter Zijlstra <peterz@infradead.org>
To: "Liang, Kan" <kan.liang@intel.com>
Cc: "mingo@kernel.org" <mingo@kernel.org>,
"acme@infradead.org" <acme@infradead.org>,
"eranian@google.com" <eranian@google.com>,
"andi@firstfloor.org" <andi@firstfloor.org>,
"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: Tue, 5 May 2015 19:00:47 +0200 [thread overview]
Message-ID: <20150505170047.GP23123@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F0770180BC7E@SHSMSX103.ccr.corp.intel.com>
On Tue, May 05, 2015 at 04:36:51PM +0000, Liang, Kan wrote:
> > > RECORDs are generic, and should live in the core code.
> > >
> > > Also, you should introduce this RECORD in a separate patch.
> >
> > On that, this is lacking a RECORD definition in
> > include/uapi/linux/perf_event.h:perf_event_type
>
> The PERF_RECORD_LOST already defined in perf_event_type.
> Are you suggesting to add a new dedicated RECORD type, like PERF_RECORD_COLLISION?
Yes, this should be a new RECORD, LOST_SAMPLES maybe.
The thing is, LOST is about the ring-buffer running out of space, this
is very much not the case here. Reusing it like this creates the
situation where userspace cannot tell what happened, and that is a very
bad thing indeed.
What we want to convey is that we dropped/lost a (number of) sample(s).
So the objection against the RECORD_COLLISIONS name is that it names the
reason we did something, but not the something we did.
next prev parent reply other threads:[~2015-05-05 17:01 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 [this message]
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
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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