linux-kernel - Re:[PATCH] sched/rt: Decrease number of calls of push_rt_task() in push_rt

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Message-Id: <798741360060024@web12h.yandex.ru>
Date:	Tue, 05 Feb 2013 14:27:04 +0400
From:	Kirill Tkhai <tkhai@...dex.ru>
To:	Honghui Zhang <zhanghonghui@...wei.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: Re:[PATCH] sched/rt: Decrease number of calls of push_rt_task() in push_rt_tasks()



> On 2013/2/5 15:22, Kirill Tkhai wrote:
> 
>>> Suppose we have a large number of cpus(say 4096), with the last one running
>>> a low-priority task on it. Is it possible with this patch we will never reach
>>> the last cpu in case that previous cpu has complete the pulled task?
>>
>> Yes. But this patch is about several pushable tasks on the same cpu.
>>
>> Kirill
> 
> Maybe I haven't make myself understood, but in that case, there will be a higher-priority
> task in the runqueue of the pushing cpu, and a lower-priority task running in the last cpu
> which could not be preempt by push_rt_task(), I don't think it's acceptable.

Sure, I tried to prevent the fact of call of this function with locks of spinlocks etc. It may
be useful on system like 2 CPU, but it's not necessary for large systems. I'm not persist in this.

Kirill

> 
> Hans
> 
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