blk-mq: support per-distpatch_queue flush machinery
This patch supports to run one single flush machinery for
each blk-mq dispatch queue, so that:
- current init_request and exit_request callbacks can
cover flush request too, then the buggy copying way of
initializing flush request's pdu can be fixed
- flushing performance gets improved in case of multi hw-queue
In fio sync write test over virtio-blk(4 hw queues, ioengine=sync,
iodepth=64, numjobs=4, bs=4K), it is observed that througput gets
increased a lot over my test environment:
- throughput: +70% in case of virtio-blk over null_blk
- throughput: +30% in case of virtio-blk over SSD image
The multi virtqueue feature isn't merged to QEMU yet, and patches for
the feature can be found in below tree:
git://kernel.ubuntu.com/ming/qemu.git v2.1.0-mq.4
And simply passing 'num_queues=4 vectors=5' should be enough to
enable multi queue(quad queue) feature for QEMU virtio-blk.
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 53b6def1..4e7a314 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -281,26 +281,6 @@
__blk_mq_free_request(hctx, ctx, rq);
}
-/*
- * Clone all relevant state from a request that has been put on hold in
- * the flush state machine into the preallocated flush request that hangs
- * off the request queue.
- *
- * For a driver the flush request should be invisible, that's why we are
- * impersonating the original request here.
- */
-void blk_mq_clone_flush_request(struct request *flush_rq,
- struct request *orig_rq)
-{
- struct blk_mq_hw_ctx *hctx =
- orig_rq->q->mq_ops->map_queue(orig_rq->q, orig_rq->mq_ctx->cpu);
-
- flush_rq->mq_ctx = orig_rq->mq_ctx;
- flush_rq->tag = orig_rq->tag;
- memcpy(blk_mq_rq_to_pdu(flush_rq), blk_mq_rq_to_pdu(orig_rq),
- hctx->cmd_size);
-}
-
inline void __blk_mq_end_request(struct request *rq, int error)
{
blk_account_io_done(rq);
@@ -1516,12 +1496,20 @@
struct blk_mq_tag_set *set,
struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
{
+ unsigned flush_start_tag = set->queue_depth;
+
blk_mq_tag_idle(hctx);
+ if (set->ops->exit_request)
+ set->ops->exit_request(set->driver_data,
+ hctx->fq->flush_rq, hctx_idx,
+ flush_start_tag + hctx_idx);
+
if (set->ops->exit_hctx)
set->ops->exit_hctx(hctx, hctx_idx);
blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
+ blk_free_flush_queue(hctx->fq);
kfree(hctx->ctxs);
blk_mq_free_bitmap(&hctx->ctx_map);
}
@@ -1556,6 +1544,7 @@
struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
{
int node;
+ unsigned flush_start_tag = set->queue_depth;
node = hctx->numa_node;
if (node == NUMA_NO_NODE)
@@ -1594,8 +1583,23 @@
set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
goto free_bitmap;
+ hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size);
+ if (!hctx->fq)
+ goto exit_hctx;
+
+ if (set->ops->init_request &&
+ set->ops->init_request(set->driver_data,
+ hctx->fq->flush_rq, hctx_idx,
+ flush_start_tag + hctx_idx, node))
+ goto free_fq;
+
return 0;
+ free_fq:
+ kfree(hctx->fq);
+ exit_hctx:
+ if (set->ops->exit_hctx)
+ set->ops->exit_hctx(hctx, hctx_idx);
free_bitmap:
blk_mq_free_bitmap(&hctx->ctx_map);
free_ctxs:
@@ -1862,16 +1866,10 @@
blk_mq_add_queue_tag_set(set, q);
- q->fq = blk_alloc_flush_queue(q);
- if (!q->fq)
- goto err_hw_queues;
-
blk_mq_map_swqueue(q);
return q;
-err_hw_queues:
- blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
err_hw:
blk_cleanup_queue(q);
err_hctxs: