On 8/2/18 9:59 AM, Tejun Heo wrote: > 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. Just make that change a separate patch, since v3 is already applied. -- Jens Axboe
