linux-kernel - Re: Make yield_task

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Message-ID: <20080221060427.GA9159@elte.hu>
Date:	Thu, 21 Feb 2008 07:04:27 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peter@...gramming.kicks-ass.net>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Make yield_task_fair more efficient


* Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> __pick_last_entity() walks the entire tree on O(lgn) time to find the 
> rightmost entry. This patch makes the routine more efficient by 
> reducing the cost of the lookup

hm, i'm not sure we want to do this: we'd be slowing down the fastpath 
of all the other common scheduler functions, for the sake of a rarely 
used (and broken ...) API: yield. And note that an rbtree walk is not 
slow at all - if you are yielding frequently it's probably all cached.

	Ingo
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