Commit 9a212683 authored Sep 04, 2015 by Christian Borntraeger Committed by Martin Schwidefsky Oct 14, 2015

s390/dasd: mark DASD devices as non rotational



We were able to reduce the CPU overhead of big paging scenarios
when announcing our paging disks as non-rotational.
Almost all dasd devices are implemented in storage servers with
cache, raid, striping and lots of magic. There is no point in
optimizing the disk schedulers and swap code for a single platter
moving arm rotational disks. Given the complexity of the setup
and the fact that this change is mostly to disable the additional
overhead in swap code, lets keep the other functionality unchanged
and do not disable the this device as entropy source - unlike other
non-rotational devices.

Suggested-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent 1330a125

drivers/s390/block/dasd.c

+1 −0

Original line number	Original line	Diff line number	Diff line
	@@ -3030,6 +3030,7 @@ static void dasd_setup_queue(struct dasd_block *block)
	} else {		} else {
	max = block->base->discipline->max_blocks << block->s2b_shift;		max = block->base->discipline->max_blocks << block->s2b_shift;
	}		}
			queue_flag_set_unlocked(QUEUE_FLAG_NONROT, block->request_queue);
	blk_queue_logical_block_size(block->request_queue,		blk_queue_logical_block_size(block->request_queue,
	block->bp_block);		block->bp_block);
	blk_queue_max_hw_sectors(block->request_queue, max);		blk_queue_max_hw_sectors(block->request_queue, max);