Re: [PATCH 2/2] io_uring: switch cancel_hash to use per list spinlock

[Hao Xu <haoxu.linux@icloud.com>]

On 5/30/22 00:25, Jens Axboe wrote:
> On 5/29/22 10:20 AM, Hao Xu wrote:
>> From: Hao Xu <howeyxu@tencent.com>
>>
>> From: Hao Xu <howeyxu@tencent.com>
>>
>> Use per list lock for cancel_hash, this removes some completion lock
>> invocation and remove contension between different cancel_hash entries
> 
> Interesting, do you have any numbers on this?

Just Theoretically for now, I'll do some tests tomorrow. This is
actually RFC, forgot to change the subject.

> 
> Also, I'd make a hash bucket struct:
> 
> struct io_hash_bucket {
> 	spinlock_t lock;
> 	struct hlist_head list;
> };
> 
> rather than two separate structs, that'll have nicer memory locality too
> and should further improve it. Could be done as a prep patch with the
> old locking in place, making the end patch doing the per-bucket lock
> simpler as well.

Sure, if the test number make sense, I'll send v2. I'll test the
hlist_bl list as well(the comment of it says it is much slower than
normal spin_lock, but we may not care the efficiency of poll
cancellation very much?).

> 
> Hmm?
>