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Message-ID: <1331048251.11248.319.camel@twins>
Subject: Re: [RFC PATCH 5/6] implement per-cpu&per-domain state machine
 call_srcu()
From: Peter Zijlstra <peterz@infradead.org>
To: Lai Jiangshan <eag0628@gmail.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
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Date: Tue, 06 Mar 2012 16:37:31 +0100
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On Tue, 2012-03-06 at 23:26 +0800, Lai Jiangshan wrote:
> On Tue, Mar 6, 2012 at 7:16 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, 2012-03-06 at 17:57 +0800, Lai Jiangshan wrote:
> >>         srcu_head is bigger, it is worth, it provides more ability and simplify
> >>         the srcu code.
> >
> > Dubious claim.. memory footprint of various data structures is deemed
> > important. rcu_head is 16 bytes, srcu_head is 32 bytes. I think it would
> > be real nice not to have two different callback structures and not grow
> > them as large.
> 
> Also "Dubious" "simplify"?

Nah, I meant dubious. 

> bigger struct makes we can store ->check_seq in the callback, makes
> the processing simply.
> 
> bigger struct is not required here, we can use a little complex way(batches)
> to do it.

Right, just keep a callback list for each state, and once you fall off
the end process it. No need to keep per callback state.