From: Tejun Heo <tj@kernel.org>
Date: Wed, 25 Sep 2019 16:03:35 -0700
Subject: [PATCH] iocost: bump up default latency targets for hard disks
Git-commit: 7afcccafa59fb63b58f863a6c5e603a34625955b
Patch-Mainline: v5.4-rc1
References: bsc#1156419,jsc#SLE-8281

The default hard disk param sets latency targets at 50ms.  As the
default target percentiles are zero, these don't directly regulate
vrate; however, they're still used to calculate the period length -
100ms in this case.

This is excessively low.  A SATA drive with QD32 saturated with random
IOs can easily reach avg completion latency of several hundred msecs.
A period duration which is substantially lower than avg completion
latency can lead to wildly fluctuating vrate.

Let's bump up the default latency targets to 250ms so that the period
duration is sufficiently long.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.de>
---
 block/blk-iocost.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 10160de62e3b..2a3db80c1dce 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -529,8 +529,8 @@ struct iocg_wake_ctx {
 static const struct ioc_params autop[] = {
 	[AUTOP_HDD] = {
 		.qos				= {
-			[QOS_RLAT]		=         50000, /* 50ms */
-			[QOS_WLAT]		=         50000,
+			[QOS_RLAT]		=        250000, /* 250ms */
+			[QOS_WLAT]		=        250000,
 			[QOS_MIN]		= VRATE_MIN_PPM,
 			[QOS_MAX]		= VRATE_MAX_PPM,
 		},
-- 
2.16.4