On 12/17/18 5:08 AM, Ming Lei wrote:
> When requst is added to rq list of sw queue(ctx), the rq may be from
> different type of hctx, especially after multi queue mapping is introduced.
>
> So when dispach request from sw queue via blk_mq_flush_busy_ctxs() or
> blk_mq_dequeue_from_ctx(), one request belonging to other queue type of
> hctx can be dispatch to current hctx in case that read queue or poll queue
> is enabled.
>
> This patch fixes this issue by introducing per-queue-type list.
Looks good, just one comment:
> diff --git a/block/blk-mq.h b/block/blk-mq.h
> index d1ed096723fb..0973a91eb1dd 100644
> --- a/block/blk-mq.h
> +++ b/block/blk-mq.h
> @@ -12,14 +12,16 @@ struct blk_mq_ctxs {
> struct blk_mq_ctx __percpu *queue_ctx;
> };
>
> +struct blk_mq_ctx_list {
> + spinlock_t lock;
> + struct list_head rq_list;
> +} ____cacheline_aligned_in_smp;
> +
> /**
> * struct blk_mq_ctx - State for a software queue facing the submitting CPUs
> */
> struct blk_mq_ctx {
> - struct {
> - spinlock_t lock;
> - struct list_head rq_list;
> - } ____cacheline_aligned_in_smp;
> + struct blk_mq_ctx_list list[HCTX_MAX_TYPES];
Let's not make that use 3 cachelines. There is no good reason to split
these across cachelines, if we have heavy traffic to multiple of these,
then we're not going very fast anyway. So just make it:
struct {
spinlock_t lock;
struct list_head rq_list[HCTX_MAX_TYPES];
} ____cacheline_aligned_in_smp;
--
Jens Axboe
