2017-10-11 2:23 GMT+08:00 Shaohua Li <shli@xxxxxxxxxx>: > On Wed, Oct 11, 2017 at 01:35:51AM +0800, weiping zhang wrote: >> On Fri, Oct 06, 2017 at 05:56:01PM -0700, Shaohua Li wrote: >> > From: Shaohua Li <shli@xxxxxx> >> > >> > Export the latency info to user. The latency is a good sign to indicate >> > if IO is congested or not. User can use the info to make decisions like >> > adjust cgroup settings. >> Hi Shaohua, >> How to check IO congested or not by latency ? Different SSD has >> different latency especially when mixed sequence and random IO >> operatons. > > There is no magic here, you should know the SSD characteristics first. The idea > is observing the latency when the system isn't overcommited, for example, > running the workload in a one-cgroup setup, then using the observed latency to > guide configuration for multi-cgroup settings or check if IO is healthy in > cgroups. > Could you please give more detail about how to get the SSD characteristics ? I cann't find a good way to get the reasonable latency at mixed sequence , random, read, and write. Is there a value or a range represent the reasonable latency at mixed circurmastance ? Thanks Weiping
