Re: [PATCH] v4 RCU: the bloatwatch edition

Paul E. McKenney
2009-06-22T17:08:38Z

On Mon, Jun 22, 2009 at 09:30:29AM -0700, Darren Hart wrote:
> Paul E. McKenney wrote:
>> On Mon, Jun 22, 2009 at 08:29:41AM -0700, Andrew Morton wrote:
>>> On Mon, 22 Jun 2009 14:49:51 +0200 Ingo Molnar <mingo@elte.hu> wrote:
>>>
>>>> * David Howells <dhowells@redhat.com> wrote:
>>>>
>>>>> Hi Paul,
>>>>>
>>>>> Are you going to push your RCU patch for this merge window?
>>>> Andrew needs to be convinced for that to happen.
>>>>
>>> whome? I rarely have firm opinions on anything. iirc the question
>>> here was "is it worth adding another RCU implementation to save 900
>>> bytes"?
>>>
>>> I find it pretty hard to see how to come up with "yes" for that one but
>>> it's hardly a huge issue. If you guys feel otherwise then go wild.
>> Well, I do need to pull the "expedited" interface into the bloatwatch
>> version, and my update of rcutorture made me realize that I can cut
>> out a few more bytes, so I will submit an update. For what it is worth,
>> here are the opinions expressed on LKML:
>> + Ingo Molnar: good documentation, minimal RCU implementation.
>> ? Andi Kleen: will there be !SMP systems in the future?
>> + Lennert Buytenhek: there will be !SMP ARM for a long time.
>> + Paul Mundt: good idea for more-constrained SH platforms.
>> + David Howells: Acked-by. works on FRV board.
>> ? Andrew Morton: do we really need another RCU implementation?
>> Of course, I well remember programming systems with 4K of core memory
>> back in the 1970s, and therefore feel a bit guilty about sticking deep
>> embedded platforms with the increase in memory footprint represented
>> by Hierarchical RCU compared to Classic RCU. And Bloatwatch RCU is much
>> smaller and easier to understand/maintain than is Classic RCU.
>> So, again, I will forward port, optimize, test, and resubmit.
>
> IIRC, in previous threads on this topic, the Bloatwatch edition was
> expected to replace Classic RCU. If so, wouldn't that address Andrew's
> concern of "adding" another implementation?

Andrew expressed a preference for dropping Classic RCU without adding
Bloatwatch RCU. ;-)

Thanx, Paul