linux-kernel - Re: [PATCH V2 1/6] perf,core: allow invalid context events to be part of sw/hw groups

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Message-ID: <20150415172856.GA5029@twins.programming.kicks-ass.net>
Date:	Wed, 15 Apr 2015 19:28:56 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Kan Liang <kan.liang@...el.com>
Cc:	acme@...nel.org, eranian@...gle.com, andi@...stfloor.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/6] perf,core: allow invalid context events to be
 part of sw/hw groups

On Wed, Apr 15, 2015 at 03:56:11AM -0400, Kan Liang wrote:
> The event count only be read when the event is already
> sched_in.

Yeah, so no. This breaks what groups are. Group events _must_ be
co-scheduled. You cannot guarantee you can schedule events from another
PMU.

Also, I cannot see how this can possibly work, you cannot put these
things on the same event_context.

Also, how does this work wrt cpumasks, regular events are per cpu,
uncore events are per node.

There is so much broken stuff here without explanation its not funny.

Please explain how this does not completely wreck everything?
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