On Thu, May 25, 2017 at 11:42:59AM -0600, Jens Axboe wrote: > On 05/25/2017 11:24 AM, Bart Van Assche wrote: > > On Thu, 2017-05-25 at 17:09 +0800, Ming Lei wrote: > >> Another big issue is that 'srcu_struct' is very big, which shouldn't > >> be embedded into hctx, since we only have one real user of > >> BLK_MQ_F_BLOCKING. > >> > >> So I will fix that too. > > > > Hello Ming, > > > > Is something like the (untested) patch below perhaps what you had in mind? > > > > Subject: [PATCH] blk-mq: Reduce blk_mq_hw_ctx size > > > > Since the srcu structure is rather large (184 bytes on an x86-64 > > system), only allocate it if needed. > > > > Reported-by: Ming Lei <[email protected]> > > --- > > block/blk-mq.c | 13 ++++++++++++- > > include/linux/blk-mq.h | 5 +++-- > > 2 files changed, 15 insertions(+), 3 deletions(-) > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > index 1e330de4e3c5..15b7d4077638 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -2233,6 +2233,17 @@ 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 request_queue *q) > > +{ > > + BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, queue_rq_srcu) + > > + sizeof(((struct blk_mq_hw_ctx *)NULL)->queue_rq_srcu), 64) != > > + sizeof(struct blk_mq_hw_ctx)); > > + > > + return q->tag_set->flags & BLK_MQ_F_BLOCKING ? > > + sizeof(struct blk_mq_hw_ctx) : > > + offsetof(struct blk_mq_hw_ctx, queue_rq_srcu); > > +} > > + > > static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, > > struct request_queue *q) > > { > > @@ -2247,7 +2258,7 @@ 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(q), > > GFP_KERNEL, node); > > if (!hctxs[i]) > > break; > > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > > index c0d59330b5e0..8467e1f83524 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; > > }; > > Why not make it > > /* Must be the last member - see also blk_mq_hw_ctx_size(). */ > struct srcu_struct queue_rq_srcu[0];
Yeah, actually that was what I did yesterday in my local tree, will posted out today with the blk_mq_quiesce_queue() fix. Thanks, Ming
