Hello, Dennis. On Wed, Aug 01, 2018 at 11:15:41PM -0700, Dennis Zhou wrote: > From: "Dennis Zhou (Facebook)" <dennisszhou@xxxxxxxxx> > > Currently, avg_lat is calculated by accumulating the mean of every > window in a long running cumulative average. As time goes on, the metric > becomes less and less useful due to the accumulated history. > > This patch reuses the same calculation done in load averages to make the > avg_lat metric more lively. Unlike load averages, the avg only advances > when a window elapses (due to an io). Idle periods extend the most > recent window. Bucketing is used to limit the history of avg_lat by > binding it to the window size. So, the window range for 1/exp (decay > rate) is [1 min, 2.5 min) when windows elapse immediately. > > The current sample window size is exposed in the debug info to enable > calculation of the window range. > > Signed-off-by: Dennis Zhou <dennisszhou@xxxxxxxxx> > Acked-by: Tejun Heo <tj@xxxxxxxxxx> > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > Acked-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Heh, sorry about not thinking this up from the beginning but I think it'd be great to move this to blkcg core so that the stat is always available regardless of blk-iolatency. It's a really important metric and can be used for both monitoring and policy implementation. Thanks! -- tejun
