Re: [PATCH v5 1/2] io_uring: minor io_cqring_wait() optimization

Jens Axboe
2022-03-09T23:43:21Z

On 3/8/22 10:36 PM, Olivier Langlois wrote:
> On Tue, 2022-03-08 at 17:54 -0700, Jens Axboe wrote:
>> On 3/8/22 3:17 PM, Olivier Langlois wrote:
>>> Move up the block manipulating the sig variable to execute code
>>> that may encounter an error and exit first before continuing
>>> executing the rest of the function and avoid useless computations
>>
>> I don't think this is worthwhile doing. If you're hitting an error
>> in any of them, it's by definition not the fast path.
>>
> Well, by itself it is not a big improvement but it is still an
> improvement.
>
> but most importantly, it has to be considered in the context of the
> current patchset because in patch #2, the following step is to
>
> 1. acquire the napi spin lock
> 2. splice the context napi list into a local one.
> 3. release the lock
>
> If this patch is not in place before patch #2, you would need undo all
> that before returning from the sig block which would make the function
> bigger when all that is completely avoidable by accepting this patch...
>
> Both patches were together in v1 but I decided to break them apart
> thinking that this was the right thing to do...

Yeah ok, it does make sense in the context of patch 2. Thanks!

--
Jens Axboe