Re: [PATCH io_uring 02/16] io_uring/zcrx: move RQ head/tail to separate cache lines

On 8/10/26 18:35, Mina Almasry wrote:
> On Fri, Aug 7, 2026 at 6:25 AM Pavel Begunkov <[email protected]> wrote:
>>
>> RQ head and tail are currently put into the same cache line, which can
>> cause false sharing problems when refill is run on another CPU. Put them
>> into separate cache lines.
...>> +struct zcrx_rq_hdr {
>> +       u32             head ____cacheline_aligned_in_smp;
>> +       u32             tail ____cacheline_aligned_in_smp;
>> +};
>> +
>>   struct zcrx_rq {
>>          spinlock_t                      lock;
>> -       struct io_uring                 *ring;
>> +       struct zcrx_rq_hdr              *ring;
> 
> Is this not a problem in general for everything/most/a lot of using
> struct io_uring? Should you make this change to struct io_uring
> itself?

No, io_uring headers are usually accessed by the same task,
that's unlike zcrx where the consumer and the producer are
two distinct entities.

-- 
Pavel Begunkov