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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>
This commit is contained in:
Christian Borntraeger 2015-09-04 13:52:44 +02:00 committed by Martin Schwidefsky
parent 1330a1258d
commit 9a21268360
1 changed files with 1 additions and 0 deletions
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1
drivers/s390/block/dasd.c
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@ -3030,6 +3030,7 @@ static void dasd_setup_queue(struct dasd_block *block)
} else {
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,
block->bp_block);
blk_queue_max_hw_sectors(block->request_queue, max);