Re: [PATCH] blk-mq: respect rq_affinity

[Jens Axboe <axboe@kernel.dk>]

On 04/25/2014 03:32 AM, Christoph Hellwig wrote:
> From: Christoph Hellwig <hch@lst.de>
> 
> The blk-mq code is using it's own version of the I/O completion affinity
> tunables, which causes a few issues:
> 
>  - the rq_affinity sysfs file doesn't work for blk-mq devices, even if it
>    still is present, thus breaking existing tuning setups.
>  - the rq_affinity = 1 mode, which is the defauly for legacy request based
>    drivers isn't implemented at all.
>  - blk-mq drivers don't implement any completion affinity with the default
>    flag settings.
> 
> This patches removes the blk-mq ipi_redirect flag and sysfs file, as well
> as the internal BLK_MQ_F_SHOULD_IPI flag and replaces it with code that
> respects the queue-wide rq_affinity flags and also implements the
> rq_affinity = 1 mode.
> 
> This means I/O completion affinity can now only be tuned block-queue wide
> instead of per context, which seems more sensible to me anyway.

Agree, this is a good cleanup, and there's no reason blk-mq needs its
own sysfs file for this.

-- 
Jens Axboe