On 1/23/24 11:40 AM, Bart Van Assche wrote:
> On 1/23/24 09:34, Jens Axboe wrote:
>> If we're entering request dispatch but someone else is already
>> dispatching, then just skip this dispatch. We know IO is inflight and
>> this will trigger another dispatch event for any completion. This will
>> potentially cause slightly lower queue depth for contended cases, but
>> those are slowed down anyway and this should not cause an issue.
>>
>> By itself, this patch doesn't help a whole lot, as the dispatch
>> lock contention reduction is just eating up by the same dd->lock now
> ^^^^^^^^
> Does this perhaps need to be modified into bfqd->lock?
Oops yeah indeed, I'll update the commit message.
>> struct bfq_data {
>> + struct {
>> + spinlock_t lock;
>> + } ____cacheline_aligned_in_smp;
>
> Hmm ... why is the spinlock surrounded with a struct { }? This is not
> clear to me. Otherwise this patch looks good to me.
Mostly just prep for the later patch, I can add the struct here on in
that patch. Doesn't really matter to me.
--
Jens Axboe
