From cd006509b0a93cb7ee9d9fd50ae274098997a460 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 13 Apr 2020 12:27:56 -0400 Subject: blk-iocost: account for IO size when testing latencies On each IO completion, iocost decides whether the IO met or missed its latency target. Currently, the targets are fixed numbers per IO type. While this can be good enough for loose latency targets way higher than typical completion latencies, the effect of IO size makes it difficult to tighten the latency target - a target adequate for 4k IOs might be too tight for 512k IOs and vice-versa. iocost already has all the necessary information to account for different IO sizes when testing whether the latency target is met as iocost can calculate the size vtime cost of a given IO. This patch updates the completion path to calculate the size vtime cost of the IO, deduct the nsec equivalent from the observed latency and use the adjusted value to decide whether the target is met. This makes latency targets independent from IO size and enables determining adequate latency targets with fixed size fio runs. Signed-off-by: Tejun Heo Cc: Andy Newell Signed-off-by: Jens Axboe --- block/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'block/Kconfig') diff --git a/block/Kconfig b/block/Kconfig index 3bc76bb113a0..41cb34b0fcd1 100644 --- a/block/Kconfig +++ b/block/Kconfig @@ -146,6 +146,7 @@ config BLK_CGROUP_IOLATENCY config BLK_CGROUP_IOCOST bool "Enable support for cost model based cgroup IO controller" depends on BLK_CGROUP=y + select BLK_RQ_IO_DATA_LEN select BLK_RQ_ALLOC_TIME ---help--- Enabling this option enables the .weight interface for cost -- cgit v1.2.3