block: remove some blk_mq_hw_ctx debugfs entries

Just like the blk_mq_ctx counterparts, we've got a bunch of counters
in here that are only for debugfs and are of questionnable value. They
are:

- dispatched, index of how many requests were dispatched in one go

- poll_{considered,invoked,success}, which track poll sucess rates. We're
  confident in the iopoll implementation at this point, don't bother
  tracking these.

As a bonus, this shrinks each hardware queue from 576 bytes to 512 bytes,
dropping a whole cacheline.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

block/blk-mq-debugfs.c

@@ -529,70 +529,6 @@ static int hctx_sched_tags_bitmap_show(void *data, struct seq_file *m)
 	return res;
 }
 
-static int hctx_io_poll_show(void *data, struct seq_file *m)
-{
-	struct blk_mq_hw_ctx *hctx = data;
-
-	seq_printf(m, "considered=%lu\n", hctx->poll_considered);
-	seq_printf(m, "invoked=%lu\n", hctx->poll_invoked);
-	seq_printf(m, "success=%lu\n", hctx->poll_success);
-	return 0;
-}
-
-static ssize_t hctx_io_poll_write(void *data, const char __user *buf,
-				  size_t count, loff_t *ppos)
-{
-	struct blk_mq_hw_ctx *hctx = data;
-
-	hctx->poll_considered = hctx->poll_invoked = hctx->poll_success = 0;
-	return count;
-}
-
-static int hctx_dispatched_show(void *data, struct seq_file *m)
-{
-	struct blk_mq_hw_ctx *hctx = data;
-	int i;
-
-	seq_printf(m, "%8u\t%lu\n", 0U, hctx->dispatched[0]);
-
-	for (i = 1; i < BLK_MQ_MAX_DISPATCH_ORDER - 1; i++) {
-		unsigned int d = 1U << (i - 1);
-
-		seq_printf(m, "%8u\t%lu\n", d, hctx->dispatched[i]);
-	}
-
-	seq_printf(m, "%8u+\t%lu\n", 1U << (i - 1), hctx->dispatched[i]);
-	return 0;
-}
-
-static ssize_t hctx_dispatched_write(void *data, const char __user *buf,
-				     size_t count, loff_t *ppos)
-{
-	struct blk_mq_hw_ctx *hctx = data;
-	int i;
-
-	for (i = 0; i < BLK_MQ_MAX_DISPATCH_ORDER; i++)
-		hctx->dispatched[i] = 0;
-	return count;
-}
-
-static int hctx_queued_show(void *data, struct seq_file *m)
-{
-	struct blk_mq_hw_ctx *hctx = data;
-
-	seq_printf(m, "%lu\n", hctx->queued);
-	return 0;
-}
-
-static ssize_t hctx_queued_write(void *data, const char __user *buf,
-				 size_t count, loff_t *ppos)
-{
-	struct blk_mq_hw_ctx *hctx = data;
-
-	hctx->queued = 0;
-	return count;
-}
-
 static int hctx_run_show(void *data, struct seq_file *m)
 {
 	struct blk_mq_hw_ctx *hctx = data;
@@ -738,9 +674,6 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_attrs[] = {
 	{"tags_bitmap", 0400, hctx_tags_bitmap_show},
 	{"sched_tags", 0400, hctx_sched_tags_show},
 	{"sched_tags_bitmap", 0400, hctx_sched_tags_bitmap_show},
-	{"io_poll", 0600, hctx_io_poll_show, hctx_io_poll_write},
-	{"dispatched", 0600, hctx_dispatched_show, hctx_dispatched_write},
-	{"queued", 0600, hctx_queued_show, hctx_queued_write},
 	{"run", 0600, hctx_run_show, hctx_run_write},
 	{"active", 0400, hctx_active_show},
 	{"dispatch_busy", 0400, hctx_dispatch_busy_show},

block/blk-mq.c

@@ -382,7 +382,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 		}
 	}
 
-	data->hctx->queued++;
 	return rq;
 }
 
@@ -1301,14 +1300,6 @@ struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
 	return data.rq;
 }
 
-static inline unsigned int queued_to_index(unsigned int queued)
-{
-	if (!queued)
-		return 0;
-
-	return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
-}
-
 static bool __blk_mq_get_driver_tag(struct request *rq)
 {
 	struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
@@ -1632,8 +1623,6 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 	if (!list_empty(&zone_list))
 		list_splice_tail_init(&zone_list, list);
 
-	hctx->dispatched[queued_to_index(queued)]++;
-
 	/* If we didn't flush the entire list, we could have told the driver
 	 * there was more coming, but that turned out to be a lie.
 	 */
@@ -4200,14 +4189,9 @@ static int blk_mq_poll_classic(struct request_queue *q, blk_qc_t cookie,
 	long state = get_current_state();
 	int ret;
 
-	hctx->poll_considered++;
-
 	do {
-		hctx->poll_invoked++;
-
 		ret = q->mq_ops->poll(hctx);
 		if (ret > 0) {
-			hctx->poll_success++;
 			__set_current_state(TASK_RUNNING);
 			return ret;
 		}

include/linux/blk-mq.h

@@ -341,9 +341,6 @@ struct blk_mq_hw_ctx {
 	unsigned long		queued;
 	/** @run: Number of dispatched requests. */
 	unsigned long		run;
-#define BLK_MQ_MAX_DISPATCH_ORDER	7
-	/** @dispatched: Number of dispatch requests by queue. */
-	unsigned long		dispatched[BLK_MQ_MAX_DISPATCH_ORDER];
 
 	/** @numa_node: NUMA node the storage adapter has been connected to. */
 	unsigned int		numa_node;
@@ -363,13 +360,6 @@ struct blk_mq_hw_ctx {
 	/** @kobj: Kernel object for sysfs. */
 	struct kobject		kobj;
 
-	/** @poll_considered: Count times blk_mq_poll() was called. */
-	unsigned long		poll_considered;
-	/** @poll_invoked: Count how many requests blk_mq_poll() polled. */
-	unsigned long		poll_invoked;
-	/** @poll_success: Count how many polled requests were completed. */
-	unsigned long		poll_success;
-
 #ifdef CONFIG_BLK_DEBUG_FS
 	/**
 	 * @debugfs_dir: debugfs directory for this hardware queue. Named