This is a note to let you know that I've just added the patch titled
s390/dasd: fix performance drop
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
s390-dasd-fix-performance-drop.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 12d319b920fa673a4d5e7c1785c5dc82dcd15257 Mon Sep 17 00:00:00 2001
From: Stefan Haberland <sth@xxxxxxxxxxxxxxxxxx>
Date: Fri, 12 Feb 2016 14:50:52 +0100
Subject: s390/dasd: fix performance drop
From: Stefan Haberland <sth@xxxxxxxxxxxxxxxxxx>
commit 12d319b920fa673a4d5e7c1785c5dc82dcd15257 upstream.
Commit ca369d51b ("sd: Fix device-imposed transfer length limits")
introduced a new queue limit max_dev_sectors which limits the maximum
sectors for requests. The default value leads to small dasd requests
and therefor to a performance drop.
Set the max_dev_sectors value to the same value as the max_hw_sectors
to use the maximum available request size for DASD devices.
Signed-off-by: Stefan Haberland <sth@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/s390/block/dasd.c | 1 +
1 file changed, 1 insertion(+)
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -3031,6 +3031,7 @@ static void dasd_setup_queue(struct dasd
max = block->base->discipline->max_blocks << block->s2b_shift;
}
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, block->request_queue);
+ block->request_queue->limits.max_dev_sectors = max;
blk_queue_logical_block_size(block->request_queue,
block->bp_block);
blk_queue_max_hw_sectors(block->request_queue, max);
Patches currently in stable-queue which might be from sth@xxxxxxxxxxxxxxxxxx are
queue-4.4/s390-dasd-fix-performance-drop.patch
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