From 4d92a9beb39d80a7d8ff7c04ae12a10290105ae5 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 29 May 2014 08:09:00 -0600 Subject: block: remove 'magic' from struct blk_plug I don't think we've ever caught any bugs with this, and there's the list poisoning for the plug lists to catch uninitialized cases. So remove the magic member and save 8 bytes in the struct. Signed-off-by: Jens Axboe --- include/linux/blkdev.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/blkdev.h') diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 913f1c2d3be0..098304576d51 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1060,7 +1060,6 @@ static inline void blk_post_runtime_resume(struct request_queue *q, int err) {} * schedule() where blk_schedule_flush_plug() is called. */ struct blk_plug { - unsigned long magic; /* detect uninitialized use-cases */ struct list_head list; /* requests */ struct list_head mq_list; /* blk-mq requests */ struct list_head cb_list; /* md requires an unplug callback */ -- cgit v1.2.3 From 05f1dd5315217398fc8d122bdee80f96a9f21274 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 29 May 2014 09:53:32 -0600 Subject: block: add queue flag for disabling SG merging If devices are not SG starved, we waste a lot of time potentially collapsing SG segments. Enough that 1.5% of the CPU time goes to this, at only 400K IOPS. Add a queue flag, QUEUE_FLAG_NO_SG_MERGE, which just returns the number of vectors in a bio instead of looping over all segments and checking for collapsible ones. Add a BLK_MQ_F_SG_MERGE flag so that drivers can opt-in on the sg merging, if they so desire. Signed-off-by: Jens Axboe --- include/linux/blkdev.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/blkdev.h') diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 098304576d51..695b9fd41efe 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -510,6 +510,7 @@ struct request_queue { #define QUEUE_FLAG_SAME_FORCE 18 /* force complete on same CPU */ #define QUEUE_FLAG_DEAD 19 /* queue tear-down finished */ #define QUEUE_FLAG_INIT_DONE 20 /* queue is initialized */ +#define QUEUE_FLAG_NO_SG_MERGE 21 /* don't attempt to merge SG segments*/ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ -- cgit v1.2.3