One approach might be to std::max(time_in_microseconds, std::numeric_limits<base::HistogramBase::Sample>::max()); another might be to replace the histogram with one whose units are less likely to overflow (but this would lose precision).

Assigning to nhiroki@, the owner of this histogram.

From comment #0 it sounds like the bug isn't that the recorded value is overflowing, it's that the histogram is being logged more times than we can handle?

bcwhite: I wonder if this is really P3, is overflowing benign? Does it have side-effects, indicate perf issues, or mean we can't trust the data?

The metric was added in 2016 in https://bugs.chromium.org/p/chromium/issues/detail?id=616721#c6, it seems maybe we can just delete the metric if we're not using it anymore.

Limiting the add amount won't really help because it's the total adds between reporting intervals that causes the overflow.

In other instances where Bytes were being counted, we changed them to KiB with probabilistic rounding so that small increments still got counted.  I'm in the process of making that reusable; I could add an "AddKilo" that does the same thing.  You still lose precision but accuracy shouldn't change significantly.

The oveflow is benign except that it gets reported (work for me) and causes 4B differences in counts on your own histograms.  So really, it mostly impacts you and those reading your histograms.

I've just landed
https://chromium-review.googlesource.com/c/chromium/src/+/905148

Which adds AddScaled(), AddKilo(), and AddKiB() methods in the base histogram class to increment the count by a scaled amount.  Precision is lost but accuracy is maintained.

You can't just change the Add* method used, though; the name of the histogram needs to be changed (add a "K" suffix?) to avoid confusion.

We will probably delete this as it's not currently being used and seems like it can give misleading data due to the overflow.

I'll go ahead and remove it.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0335b2141d9938dfb8417f600165fcc9b2addf17

commit 0335b2141d9938dfb8417f600165fcc9b2addf17
Author: Matt Falkenhagen <falken@chromium.org>
Date: Tue Feb 13 06:09:00 2018

Remove WorkerThread.Task.Time histogram.

This is overflowing causing confusion. Since we don't use it we can
delete it. Also delete the related histogram
WorkerThread.DebuggerTask.Time.

Bug:  616721 , 809672 
Change-Id: I33895fdf033ab2c07ccecfb05c75085a45569011
Reviewed-on: https://chromium-review.googlesource.com/911229
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536264}
[modify] https://crrev.com/0335b2141d9938dfb8417f600165fcc9b2addf17/third_party/WebKit/Source/core/workers/WorkerThread.cpp
[modify] https://crrev.com/0335b2141d9938dfb8417f600165fcc9b2addf17/third_party/WebKit/Source/platform/scheduler/child/worker_scheduler_impl.cc
[modify] https://crrev.com/0335b2141d9938dfb8417f600165fcc9b2addf17/tools/metrics/histograms/histograms.xml

bcwhite: thanks for reporting and adding the new APIs.