Re: [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled

Kirill Tkhai
2018-08-08T16:23:17Z

On 08.08.2018 19:13, Josh Triplett wrote:
> On Wed, Aug 08, 2018 at 01:17:44PM +0300, Kirill Tkhai wrote:
>> On 08.08.2018 10:20, Michal Hocko wrote:
>>> On Tue 07-08-18 18:37:36, Kirill Tkhai wrote:
>>>> This patch kills all CONFIG_SRCU defines and
>>>> the code under !CONFIG_SRCU.
>>>
>>> The last time somebody tried to do this there was a pushback due to
>>> kernel tinyfication. So this should really give some numbers about the
>>> code size increase. Also why can't we make this depend on MMU. Is
>>> anybody else than the reclaim asking for unconditional SRCU usage?
>>
>> I don't know one. The size numbers (sparc64) are:
>>
>> $ size image.srcu.disabled
>> text data bss dec hex filename
>> 5117546 8030506 1968104 15116156 e6a77c image.srcu.disabled
>> $ size image.srcu.enabled
>> text data bss dec hex filename
>> 5126175 8064346 1968104 15158625 e74d61 image.srcu.enabled
>> The difference is: 15158625-15116156 = 42469 ~41Kb
>
> 41k is a *substantial* size increase. However, can you compare
> tinyconfig with and without this patch? That may have a smaller change.

$ size image.srcu.disabled
text data bss dec hex filename
1105900 195456 63232 1364588 14d26c image.srcu.disabled

$ size image.srcu.enabled
text data bss dec hex filename
1106960 195528 63232 1365720 14d6d8 image.srcu.enabled

1365720-1364588 = 1132 ~ 1Kb