Re: [PATCH 12/13] io_uring: cache task struct refs

[Pavel Begunkov <asml.silence@xxxxxxxxx>]

On 5/27/21 10:51 PM, Noah Goldstein wrote:
> On Mon, May 24, 2021 at 7:51 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote:
[...]
>>
>> -       percpu_counter_add(&current->io_uring->inflight, nr);
>> -       refcount_add(nr, &current->usage);
>> +       tctx = current->io_uring;
>> +       tctx->cached_refs -= nr;
>> +       if (unlikely(tctx->cached_refs < 0)) {
>> +               unsigned int refill = -tctx->cached_refs + IO_TCTX_REFS_CACHE_NR;
> 
> Might be cleared to use:
> 
> unsigned int refill =  IO_TCTX_REFS_CACHE_NR - tctx->cached_refs;

=======================================================================
Did think about it, but left as is to emphasize that it's negative and
we convert it to positive, so all operations are with positive (and
unsigned due to C rules). Code generation will be same.


>> +
>> +               percpu_counter_add(&tctx->inflight, refill);
>> +               refcount_add(refill, &current->usage);
>> +               tctx->cached_refs += refill;
>> +       }
>>         io_submit_state_start(&ctx->submit_state, nr);
>>

-- 
Pavel Begunkov