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?
> 
> 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.
> 
> Hmm?
> 

I've done a v2 here, also a test which issues async poll densely to
make high frequency cancel_hash[] visits. But I won't have a real box
with big number of cpu processors which is suitable for testing until
tomorrow, so I'd test it tomorrow.

https://github.com/HowHsu/linux/commits/for-5.20/io_uring_hash_lock

https://github.com/HowHsu/liburing/commit/b9fb4d20a5dfe7c7bd62fe36c37aea3b261d4499