Re: [Qemu-devel] [PATCH v2 1/2] block/accounting: introduce latency histogram

[Eric Blake]

On 03/08/2018 12:58 PM, Vladimir Sementsov-Ogievskiy wrote:
> > > Hm. these numbers are actually boundary points of histogram 
> > > intervals, not intervals itself. And, wiki says "The bins are usually 
> > > specified as consecutive, non-overlapping intervals of a variable.", 
> > > so, intervals are bins.
> > >
> > > So, what about:
> > >
> > > 1. interval_boundaries
> > > 2. bin_boundaries
> > > 3. boundaries
> > >
> > > (and same names with s/_/-/ for qapi)

Any of those works for me; 1 is probably most precise, while 3 is the 
shortest to type.

> > >
> >
> >
> > Also, now I doubt, is it a good idea to share same bin boundaries for 
> > each io type.
>
> so, for qmp command, what about:
>
> boundaries - optional, default boundaries for all io operations
> boundaries-read - boundaries for read
> boundaries-write - boundaries for write
> ...
>
> so, call without any boundaries: drop _all_ histograms
> call with only specific boundaries-*: set or reset _only_ corresponding 
> specific histograms
> call with only boundaries parameter: set or reset _all_ histograms
> call with boundaries parameter and some of (or all, but it is not 
> useful) specific boundaries-*: set or reset _all_ histograms, some to 
> default  and some to specific.

Seems reasonable, and if that makes the command more useful for your 
timing, I'm fine with it (your argument that different timing bins for 
read and write also makes sense, as there are some inherent differences 
in the amount of work done in the two directions).

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org