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Date: Thu, 16 Apr 2015 17:43:57 +0100 From: Mark Rutland <mark.rutland@....com> To: Kan Liang <kan.liang@...el.com> Cc: "acme@...nel.org" <acme@...nel.org>, "a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>, "eranian@...gle.com" <eranian@...gle.com>, "andi@...stfloor.org" <andi@...stfloor.org>, "linux-kernel@...r.kernel.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 > Even if you ignore the fundamental semantics of groups, there are other > problems with allowing shared contexts: > > * The *_txn functions only get called on the group leader's PMU. If your > system PMU has these functions, they are not called. > > * Event rotation is per ctx, but now you could have some events in a CPU > PMU's context, and some in the uncore PMU's context. So those can race > with each other. > > * Throttling is also per-context. So those can race with each other too. There's also a break down of behaviour: events in the uncore context will get migrated to another CPU in the event of a hot unplug, while events that are grouped with CPU events (and hence live in the CPU context) will be destroyed. Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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