Re: [PATCH] signal: Allow RT tasks to cache one sigqueue struct

[Thomas Gleixner]

On Thu, Mar 11 2021 at 13:45, Thomas Gleixner wrote:

> On Thu, Mar 11 2021 at 00:56, Thomas Gleixner wrote:
>> Rant aside, there is no massive benefit of doing that caching in
>> general, but there is not much of a downside either and for particular
>> use cases it's useful even outside of PREEMPT_RT.
>>
>> IMO, having it there unconditionally is better than yet another special
>> cased hackery.
>
> Just did some micro instrumentation to measure the time spent in
> __sigqueue_alloc/free() with and without the caching.
>
> Unsurprisingly that results in a time reduction of ~67% saving about 3us
> per alloc/free pair. Not hugely relevant for a kernel build but for
> anything which is signal heavy it'll make an difference.

That's all fastpath allocations and nothing which hit the slow path,
which would be way worse.

Thanks,

        tglx