[Engine-devel] [UX] how to design a bar/line chart?

[Lior Vernia]

On 06/11/13 16:26, Einav Cohen wrote:
> Hi Tomas,
> 
> Like Itamar, I think that a line chart is a better idea, and that a 
> chart per monitored fact (rather than a combined chart) is better.
> 
>>> the statistics readable enough. Maybe if you hover the chart it could pop
>>> up a bigger version of the chart? Or not needed?
> 
> this is a nice-to-have, I think, definitely not needed.
> 
>>> - Would it be enough to have it in one color? Or should it be something
>>> like "the bigger the utilization the more red"?
> 
> question is what will happen when there are a lot of "jumps": let's say 
> that the graph changes from 0% to 100% to 0% to 100% and so on... what 
> will be painted red? the entire line, but only in the periods that it 
> jumps to 100%? only the parts of line that are in 100%?
> maybe a single color is enough.
> 
> I have another concern about this feature: currently, the GUI's most frequent 
> refresh rate available is 5 seconds, which means that the line will "change" 
> only every 5 seconds, which would be more noticeably slow when displayed in 
> a form of a line chart (not even talking about lower frequencies).
> Moreover, I am not sure at what rate the VM statistics are pulled from VDSM, 
> but if it is 10 seconds or 15 seconds, it means that the line in the GUI will 
> be "flat" for every 2 reads / 3 reads, which is not so good, I think.
> 
> any thoughts around that?
> 

If this is indeed an issue, it could be easily solved by delaying the
presentation of the value obtained from VDSM, and at each moment present
a linear interpolation of the value between the previous input and the
current input.

Formally put, let's say T is the measurement period time. If the value
at time t is f(t), then at time t-T <= t' <= T we would display the
value f(t-2T) + [f(t-T) - f(t-2T]*t'/T, where we control the increment
rate of t'.

For example, let's say we get a new value from VDSM every 15 seconds. 30
seconds ago the CPU usage was 50MB, 15 seconds ago 100MB and now 200MB.
We decided to update the graph every 3 seconds.

15 seconds ago we displayed 50MB (the value from 30 seconds ago). 12
seconds ago we displayed 60MB, 9 seconds ago 70MB, 6 seconds ago 80MB, 3
seconds ago 90MB, and now we display 100MB (which is again late by 15
seconds). We will only display 200MB in 15 seconds, after increasing our
displayed value by 20MB every 3 seconds.

> ----- Original Message -----
>> From: "Itamar Heim" <iheim at redhat.com>
>> To: "Tomas Jelinek" <tjelinek at redhat.com>, "engine-devel" <engine-devel at ovirt.org>
>> Sent: Tuesday, November 5, 2013 10:10:34 AM
>> Subject: Re: [Engine-devel] [UX] how to design a bar/line chart?
>>
>> On 11/05/2013 11:50 AM, Tomas Jelinek wrote:
>>> Hi all,
>>>
>>> There is a feature request [1] which aims to replace the resource
>>> utilization graphs (for example the cpu utilization from vm tab) by some
>>> which shows not only
>>> the actual percentage which is not so useful by some monitor graph.
>>>
>>> I have the following concerns:
>>> - I can think of a bar chart or a line chart and not sure what would be
>>> better.
>>> - Not sure if replacing the current chart with a bar/line chart would make
>>> the statistics readable enough. Maybe if you hover the chart it could pop
>>> up a bigger version of the chart? Or not needed?
>>> - Would it be enough to have it in one color? Or should it be something
>>> like "the bigger the utilization the more red"?
>>>
>>> Please advise from the UX perspective. As soon as the final design will be
>>> a bit more clear I will provide a feature page.
>>>
>>> Thank you,
>>> Tomas
>>>
>>> [1]: https://bugzilla.redhat.com/show_bug.cgi?id=803251
>>> _______________________________________________
>>> Engine-devel mailing list
>>> Engine-devel at ovirt.org
>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
>>>
>>
>> a moving trend graph (just like fedora's system monitor for
>> cpu/ram/network) is what i have in mind. so a line chart.
>> you could have a single chart with different lines for cpu/ram/network,
>> or what seems to be more common, a chart per monitored fact
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>>
>>
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