linux-kernel - Re: [RFC PATCH 5/5 single-thread-version] implement per-domain single-thread state machine call

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Date:	Wed, 14 Mar 2012 15:47:06 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	Lai Jiangshan <eag0628@...il.com>, linux-kernel@...r.kernel.org,
	mingo@...e.hu, dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, darren@...art.com, fweisbec@...il.com,
	patches@...aro.org
Subject: Re: [RFC PATCH 5/5 single-thread-version] implement per-domain single-thread
 state machine call_srcu()

On 03/13/2012 02:03 AM, Paul E. McKenney wrote:

>>
>> In mb()-based srcu, synchronize_srcu() is very fast,
>> synchronize_srcu_expedited() makes less sense than before.
> 
> I am worried about expedited callbacks getting backed up behind
> non-expedited callbacks (especially given Peter's point about per-VMA
> SRCU callbacks) and behind other workqueue uses.
> 
>> But when wait_srcu_gp() is move back here, I will use
>> a bigger "trycount" for synchronize_srcu_expedited().
>>
>> And any problem for srcu_advance_batches()?
> 
> I prefer the use of "return" that you and Peter discussed later.
> 
> What sort of testing are you doing?
>

rcutorture in my box for several days on my daily used machine.

What would you prefer for next round of patches, single-thread or per-cpu?
I will send them soon.
(per-cpu approach will be also "batches, in-sleepable, reuse rcu_head"....)

I prefer the single-thread approach until high-callback-rate-per-domain-era
comes, but I don't know how long when it comes. Peter?

Thanks,
Lai
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