path: root/Documentation/block/queue-sysfs.txt
diff options
authorShaohua Li <>2017-03-27 10:51:37 -0700
committerJens Axboe <>2017-03-28 08:02:20 -0600
commit297e3d854784821d3b8ff3ae117f20d71f125504 (patch)
tree1909a3ce719f5a434d4e4e7584424b3559738be0 /Documentation/block/queue-sysfs.txt
parent06cceedcca67a93ac7f7aa93bbd9980c7496d14e (diff)
blk-throttle: make throtl_slice tunable
throtl_slice is important for blk-throttling. It's called slice internally but it really is a time window blk-throttling samples data. blk-throttling will make decision based on the samplings. An example is bandwidth measurement. A cgroup's bandwidth is measured in the time interval of throtl_slice. A small throtl_slice meanse cgroups have smoother throughput but burn more CPUs. It has 100ms default value, which is not appropriate for all disks. A fast SSD can dispatch a lot of IOs in 100ms. This patch makes it tunable. Since throtl_slice isn't a time slice, the sysfs name 'throttle_sample_time' reflects its character better. Signed-off-by: Shaohua Li <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'Documentation/block/queue-sysfs.txt')
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index c0a3bb5a6e4e..b7f6bdc96d73 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -192,5 +192,11 @@ scaling back writes. Writing a value of '0' to this file disables the
feature. Writing a value of '-1' to this file resets the value to the
default setting.
+throttle_sample_time (RW)
+This is the time window that blk-throttle samples data, in millisecond.
+blk-throttle makes decision based on the samplings. Lower time means cgroups
+have more smooth throughput, but higher CPU overhead. This exists only when
Jens Axboe <>, February 2009