[PATCH v4 01/12] blk-mq: Reduce blk_mq_hw_ctx size
From: Bart Van Assche <hidden>
Date: 2017-06-19 22:07:50
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
From: Bart Van Assche <redacted> Since the srcu structure is rather large (184 bytes on an x86-64 system with kernel debugging disabled), only allocate it if needed. Reported-by: Ming Lei <redacted> Signed-off-by: Bart Van Assche <redacted> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Ming Lei <redacted> Cc: Hannes Reinecke <hare@suse.com> Cc: Omar Sandoval <redacted> --- block/blk-mq.c | 30 ++++++++++++++++++++++-------- include/linux/blk-mq.h | 5 +++-- 2 files changed, 25 insertions(+), 10 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 80b14457cf6c..2dff85cdacba 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c@@ -186,7 +186,7 @@ void blk_mq_quiesce_queue(struct request_queue *q) queue_for_each_hw_ctx(q, hctx, i) { if (hctx->flags & BLK_MQ_F_BLOCKING) - synchronize_srcu(&hctx->queue_rq_srcu); + synchronize_srcu(hctx->queue_rq_srcu); else rcu = true; }
@@ -1106,9 +1106,9 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) } else { might_sleep(); - srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu); + srcu_idx = srcu_read_lock(hctx->queue_rq_srcu); blk_mq_sched_dispatch_requests(hctx); - srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx); + srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx); } }
@@ -1517,9 +1517,9 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, might_sleep(); - srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu); + srcu_idx = srcu_read_lock(hctx->queue_rq_srcu); __blk_mq_try_issue_directly(hctx, rq, cookie, true); - srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx); + srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx); } }
@@ -1863,7 +1863,7 @@ static void blk_mq_exit_hctx(struct request_queue *q, set->ops->exit_hctx(hctx, hctx_idx); if (hctx->flags & BLK_MQ_F_BLOCKING) - cleanup_srcu_struct(&hctx->queue_rq_srcu); + cleanup_srcu_struct(hctx->queue_rq_srcu); blk_mq_remove_cpuhp(hctx); blk_free_flush_queue(hctx->fq);
@@ -1936,7 +1936,7 @@ static int blk_mq_init_hctx(struct request_queue *q, goto free_fq; if (hctx->flags & BLK_MQ_F_BLOCKING) - init_srcu_struct(&hctx->queue_rq_srcu); + init_srcu_struct(hctx->queue_rq_srcu); blk_mq_debugfs_register_hctx(q, hctx);
@@ -2211,6 +2211,20 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set) } EXPORT_SYMBOL(blk_mq_init_queue); +static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set) +{ + int hw_ctx_size = sizeof(struct blk_mq_hw_ctx); + + BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, queue_rq_srcu), + __alignof__(struct blk_mq_hw_ctx)) != + sizeof(struct blk_mq_hw_ctx)); + + if (tag_set->flags & BLK_MQ_F_BLOCKING) + hw_ctx_size += sizeof(struct srcu_struct); + + return hw_ctx_size; +} + static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, struct request_queue *q) {
@@ -2225,7 +2239,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, continue; node = blk_mq_hw_queue_to_node(q->mq_map, i); - hctxs[i] = kzalloc_node(sizeof(struct blk_mq_hw_ctx), + hctxs[i] = kzalloc_node(blk_mq_hw_ctx_size(set), GFP_KERNEL, node); if (!hctxs[i]) break;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index ed1b43045ed6..384a448a92a8 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h@@ -39,8 +39,6 @@ struct blk_mq_hw_ctx { struct blk_mq_tags *tags; struct blk_mq_tags *sched_tags; - struct srcu_struct queue_rq_srcu; - unsigned long queued; unsigned long run; #define BLK_MQ_MAX_DISPATCH_ORDER 7
@@ -62,6 +60,9 @@ struct blk_mq_hw_ctx { struct dentry *debugfs_dir; struct dentry *sched_debugfs_dir; #endif + + /* Must be the last member - see also blk_mq_hw_ctx_size(). */ + struct srcu_struct queue_rq_srcu[0]; }; struct blk_mq_tag_set {
--
2.13.1