Commit 38535201 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

blk-mq: respect rq_affinity 



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.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 87ee7b11

block/blk-mq-sysfs.c

+0 −42
Original line number Diff line number Diff line
@@ -203,42 +203,6 @@ static ssize_t blk_mq_hw_sysfs_rq_list_show(struct blk_mq_hw_ctx *hctx, 
	return ret;

}



static ssize_t blk_mq_hw_sysfs_ipi_show(struct blk_mq_hw_ctx *hctx, char *page)

{

	ssize_t ret;



	spin_lock(&hctx->lock);

	ret = sprintf(page, "%u\n", !!(hctx->flags & BLK_MQ_F_SHOULD_IPI));

	spin_unlock(&hctx->lock);



	return ret;

}



static ssize_t blk_mq_hw_sysfs_ipi_store(struct blk_mq_hw_ctx *hctx,

					 const char *page, size_t len)

{

	struct blk_mq_ctx *ctx;

	unsigned long ret;

	unsigned int i;



	if (kstrtoul(page, 10, &ret)) {

		pr_err("blk-mq-sysfs: invalid input '%s'\n", page);

		return -EINVAL;

	}



	spin_lock(&hctx->lock);

	if (ret)

		hctx->flags |= BLK_MQ_F_SHOULD_IPI;

	else

		hctx->flags &= ~BLK_MQ_F_SHOULD_IPI;

	spin_unlock(&hctx->lock);



	hctx_for_each_ctx(hctx, ctx, i)

		ctx->ipi_redirect = !!ret;



	return len;

}



static ssize_t blk_mq_hw_sysfs_tags_show(struct blk_mq_hw_ctx *hctx, char *page)

{

	return blk_mq_tag_sysfs_show(hctx->tags, page);
@@ -307,11 +271,6 @@ static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_pending = { 
	.attr = {.name = "pending", .mode = S_IRUGO },

	.show = blk_mq_hw_sysfs_rq_list_show,

};

static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_ipi = {

	.attr = {.name = "ipi_redirect", .mode = S_IRUGO | S_IWUSR},

	.show = blk_mq_hw_sysfs_ipi_show,

	.store = blk_mq_hw_sysfs_ipi_store,

};

static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_tags = {

	.attr = {.name = "tags", .mode = S_IRUGO },

	.show = blk_mq_hw_sysfs_tags_show,
@@ -326,7 +285,6 @@ static struct attribute *default_hw_ctx_attrs[] = { 
	&blk_mq_hw_sysfs_run.attr,

	&blk_mq_hw_sysfs_dispatched.attr,

	&blk_mq_hw_sysfs_pending.attr,

	&blk_mq_hw_sysfs_ipi.attr,

	&blk_mq_hw_sysfs_tags.attr,

	&blk_mq_hw_sysfs_cpus.attr,

	NULL,

block/blk-mq.c

+6 −2
Original line number Diff line number Diff line
@@ -326,15 +326,19 @@ static void __blk_mq_complete_request_remote(void *data) 
void __blk_mq_complete_request(struct request *rq)

{

	struct blk_mq_ctx *ctx = rq->mq_ctx;

	bool shared = false;

	int cpu;



	if (!ctx->ipi_redirect) {

	if (!test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags)) {

		rq->q->softirq_done_fn(rq);

		return;

	}



	cpu = get_cpu();

	if (cpu != ctx->cpu && cpu_online(ctx->cpu)) {

	if (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags))

		shared = cpus_share_cache(cpu, ctx->cpu);



	if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {

		rq->csd.func = __blk_mq_complete_request_remote;

		rq->csd.info = rq;

		rq->csd.flags = 0;

block/blk-mq.h

+0 −1
Original line number Diff line number Diff line
@@ -11,7 +11,6 @@ struct blk_mq_ctx { 


	unsigned int		cpu;

	unsigned int		index_hw;

	unsigned int		ipi_redirect;



	/* incremented at dispatch time */

	unsigned long		rq_dispatched[2];

include/linux/blk-mq.h

+0 −1
Original line number Diff line number Diff line
@@ -122,7 +122,6 @@ enum { 


	BLK_MQ_F_SHOULD_MERGE	= 1 << 0,

	BLK_MQ_F_SHOULD_SORT	= 1 << 1,

	BLK_MQ_F_SHOULD_IPI	= 1 << 2,



	BLK_MQ_S_STOPPED	= 0,

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