iocost: bump up default latency targets for hard disks

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>

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 10160de62e3b48b77c30430f38c35c658b49c5b0..2a3db80c1dce7f97c65229510d078e3553615fc4 100644 (file)
--- 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,
                },