966755 - Network statistics report wrong total download times

Status: RESOLVED FIXED

(DevTools :: Netmonitor, defect)

Description

[Girish Sharma [:Optimizer]]

See this screenshot : http://i.snag.gy/pCTjR.jpg

In both the charts, divide the Total size / time taken to get download speed.

It gives 10MBps and ~9MBps in this case.

My internet speed is actually 8mbps. Notice the small mb making the actual download speed to be 1MBps.

Is there a catch to those numbers ? If not, then they are being over reported.

Comment 1

[Victor Porof [:vporof][:vp]]

There are many factors that can affect these numbers, like not all downloads being made simultaneously, nor consecutively, not in any kind of deterministic way. Summing up things is a bad way to ascertain network bandwidth.

Comment 2

[Girish Sharma [:Optimizer]]

However parallel the downloads happen, my download speed is restricted by my ISP and my plan. It can never exceed that limit. Not by ten folds.

I beg to differ that this is invalid, or some massive optimization/parallelism or some other factor increased my download speed by 10 folds.

It might be that we are getting some wrong data by the necko layer, but then, the normal network waterfall gives accurate time and size, so that is that.

I think there should be more information provided on what the "Time" field is displaying.

See this screenshot - http://i.snag.gy/1153r.jpg . Some of the resources are taking more than 500ms. [This is with cache disabled]

Now for the same page, I check the network statistics - http://i.snag.gy/hipFu.jpg

It says that "Time" is 72.41ms . Is it the average time taken to download each resource ? What is it ?

It definitely cannot be total cumulative time taken to download all resources.

After debugging through, I saw that in netmonitor-view.js:2453 you divide the total time for each type of resource by 1000, making the total time in "Seconds" but the chart says it is "ms". I think that is the main issue.

Comment 3

[Victor Porof [:vporof][:vp]]

It's not seconds, it's milliseconds. The same division is made to display the time in the waterfall. Even more, if it really was seconds, that would mean that pages take one or two minutes to download on my machine :)

Comment 4

[Victor Porof [:vporof][:vp]]

It actually *is* seconds!

Comment 5

[Girish Sharma [:Optimizer]]

Attachment: ms->seconds

Fixed the string, both key and value.

Comment 6

[Victor Porof [:vporof][:vp]]

Comment on attachment 8369213 [details] [diff] [review]
ms->seconds

Review of attachment 8369213 [details] [diff] [review]:
-----------------------------------------------------------------

r+ with the below change.

::: browser/locales/en-US/chrome/browser/devtools/netmonitor.properties
@@ +171,5 @@
>  charts.totalSize=Size: %S KB
>  
>  # LOCALIZATION NOTE (charts.totalTime): This is the label displayed
> +# in the performance analysis view for total requests time, in seconds.
> +charts.totalTime=Time: %S seconds

Should change this string's name too.

Comment 7

[Girish Sharma [:Optimizer]]

Attachment: ms->seconds2

done. and changed the string "seconds" to "s" for the table, as suggested on IRC.

Comment 8

[Victor Porof [:vporof][:vp]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/6990058bde98

Comment 9

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/6990058bde98