Re: [RFC PATCH 3/3] blk-mq: Remove generation seqeunce

Jens Axboe
2018-05-22T03:16:33Z

On 5/21/18 8:49 PM, Ming Lei wrote:
> On Mon, May 21, 2018 at 05:11:31PM -0600, Keith Busch wrote:
>> This patch simplifies the timeout handling by relying on the request
>> reference counting to ensure the iterator is operating on an inflight
>
> The reference counting isn't free, what is the real benefit in this way?

Neither is the current scheme and locking, and this is a hell of a lot
simpler. I'd get rid of the kref stuff and just do a simple
atomic_dec_and_test(). Most of the time we should be uncontended on
that, which would make it pretty darn cheap. I'd be surprised if it
wasn't better than the current alternatives.

--
Jens Axboe