linux-kernel - Re: [PATCH] perf_events: fix and improve x86 event scheduling

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Date:	Thu, 10 Nov 2011 19:41:59 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Robert Richter <robert.richter@....com>
Cc:	Stephane Eranian <eranian@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ming.m.lin@...el.com" <ming.m.lin@...el.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: Re: [PATCH] perf_events: fix and improve x86 event scheduling

On Thu, 2011-11-10 at 19:03 +0100, Robert Richter wrote:
> But this algorithm does not work for all cases and does not solve the
> problem in general. 

Yeah, the problem in general is O(n!) no O(n^3) algorithm can compute
the optimal solution for n>3 or so.

I think the goal is to keep the 'normal' case O(n^2) but try and suck
less for the corner cases without degenerating into a full blown O(n!).

So I think we want an amortized O(n^2) with an upper bound well below
O(n!).
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