Re: [PATCH] block: switch to atomic_t for request references

Jens Axboe
2021-12-06T16:31:29Z

On 12/5/21 11:53 PM, Christoph Hellwig wrote:
> On Fri, Dec 03, 2021 at 08:35:40AM -0700, Jens Axboe wrote:
>> refcount_t is not as expensive as it used to be, but it's still more
>> expensive than the io_uring method of using atomic_t and just checking
>> for potential over/underflow.
>>
>> This borrows that same implementation, which in turn is based on the
>> mm implementation from Linus.
>
> If refcount_t isn't good enough for a normal kernel fast path we have
> a problem. Can we discuss that with the maintainers instead of coming
> up with our home grown schemes again?

I think what needs to happen next here is that the code is put into a
separate header so that the vm, io_uring, and block can all use it.
refcount_t is better than it used to be, but there's a difference
between fast path and tens of millions of inc/decs per second.

--
Jens Axboe