Re: [PATCH 3/9] writeback: bdi write bandwidth estimation

Wu Fengguang
2011-07-23T08:07:41Z

On Sat, Jul 02, 2011 at 03:29:15AM +0800, Vivek Goyal wrote:
> On Wed, Jun 29, 2011 at 10:52:48PM +0800, Wu Fengguang wrote:
> > The estimation value will start from 100MB/s and adapt to the real
> > bandwidth in seconds.
> >
> > It tries to update the bandwidth only when disk is fully utilized.
> > Any inactive period of more than one second will be skipped.
>
> Is this piece of code being tested in your graphs? Are there any
> inactive periods which get filtered out in your workload? I am
> assuming in a continuous dd, we will not have periods of inactivity
> 1 second long.

There are no inactive periods in the dd tests. However I did try
"watch cat /debug/bdi/8:0/stats" while starting some write workloads
in background. When the write stops, the bandwidth does stop updating.

Thanks,
Fengguang