Status: Assigned
Owner: [email protected]
Labels: Type-Bug Pri-2 OS-All Area-Misc Size-Medium

New issue 14678 by [email protected]: RequestToFinish histogram has  
incorrect data
http://code.google.com/p/chromium/issues/detail?id=14678

There was a large change (regression?) between Google Chrome 3.0.183.x and
3.0.189.x.  Suddenly, RequestToFinish histogram is reported almost all its
samples at roughly 0.

I reviewed the code in that area, and noted that the current defintion
seems wrong, as the following two lines appear to have the same values:

  TimeDelta start_to_finish = finish_load_time - start_load_time;
  TimeDelta request_to_finish = finish_load_time - start_load_time;

Reviewing blame, the above typo landed in revision 13116 (i.e., these two
data values have been the same for a while).

In addition, the effective metric (start_to_finish and/or
request_to_finish) changed dramatically between the above two version.

I considered the possibility that my recent change in which histogram macro
was used might have caused the regression... but after staring at the code,
I'm sure it was not the cause.  In addition, the second histogram, with the
same value (due to the above typo) also changed dramatically (regressed?)
even though I didn't change its macro (which means the regression is in the
data source, not the histogram macro details).

This problem is blocking several optimization experiments, and really needs
to be looked at asap.  I could fix the above typo... but that is not the
major problem/regression.

Thanks in advance,

Jim

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