netdev - Re: [PATCH net-next 2/2] net: exit busy loop when another process is runnable

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Date:	Mon, 25 Aug 2014 10:54:41 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Mike Galbraith <umgwanakikbuti@...il.com>, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	mst@...hat.com, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, eliezer.tamir@...ux.intel.com
Subject: Re: [PATCH net-next 2/2] net: exit busy loop when another process
 is runnable

On 08/22/2014 10:16 PM, Eric Dumazet wrote:
> On Fri, 2014-08-22 at 17:08 +0800, Jason Wang wrote:
>
>> > But this is just for current process. We want to determine whether or
>> > not it was worth to loop busily in current process by checking if
>> > there's any another runnable processes or callbacks. And what we need
>> > here is just a simple and lockless hint which can't be wrong but may be
>> > inaccurate to exit the busy loop. The net code does not depends on this
>> > hint to do scheduling or yielding.
>> > 
>> > How about just introducing a boolean helper like current_can_busy_loop()
>> > and return true in one of the following conditions:
>> > 
>> > - Current task is SCHED_FIFO
>> > - Current task is neither SCHED_FIFO nor SCHED_IDLE and no other
>> > runnable processes or pending RCU callbacks in current cpu
>> > 
>> > And add warns to make sure it can only be called in process context.
> 1) Any reasons Eliezer Tamir is not included in the CC list ?
>
>    He is the busypoll author after all, and did nothing wrong to be
> banned from these patches ;)
CC Eliezer Tamir


No intentional, I just generate the CC list through get_maintainer.pl :(
>
> 2) It looks like sk_buy_loop() should not be inlined, its is already too
> big.

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