linux-kernel - Re: [RFC] perf_events: ctx_flexible_sched

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Date:	Fri, 07 May 2010 10:44:38 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>, mingo@...e.hu,
	Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC] perf_events: ctx_flexible_sched_in() not maximizing PMU
 utilization

On Fri, 2010-05-07 at 10:25 +0200, Peter Zijlstra wrote:
> We are however still fully greedy, which is still O(n), which we don't
> want. However if we stop being greedy and use the same heuristic we do
> now, stop filling the PMU at the first fail, we'll still be fair,
> because the algorithm ensures that.
> 
FWIW the non-greedy algorithm is O(m * log(n)), where m is the number of
counters on the PMU and n the number of competing events, since m is
pretty much a constant, we can say the full algorithm is O(log n).



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