Re: [PATCH v2] locking/rwsem: Add __always_inline annotation to __down_read_common()

[Waiman Long <longman@redhat.com>]

On 4/17/23 07:19, Peter Zijlstra wrote:
> On Wed, Apr 12, 2023 at 03:59:05AM +0000, John Stultz wrote:
>> Apparently despite it being marked inline, the compiler
>> may not inline __down_read_common() which makes it difficult
>> to identify the cause of lock contention, as the blocked
>> function will always be listed as __down_read_common().
>>
>> So this patch adds __always_inline annotation to the
>> function to force it to be inlines so the calling function
>> will be listed.
> I'm a wee bit confused; what are you looking at? Wchan? What is stopping
> the compiler from now handing you
> __down_read{,_interruptible,_killable}() instead? Is that fine?
>
My theory is that the compiler may refuse to inline __down_read_common() 
because it is called 3 times in order to reduce overall code size. The 
other __down_read*() functions you listed are only called once.

My 2 cents.

Cheers,
Longman