Memory overhead from collection session measurements and subsession measurements

[Vladan Djeric]

A note on implementation:

Measurements such as slowSQL, chrome-hangs, and thread-hangs are
implemented in C++ and TelemetryPing.jsm simply queries the relevant C++
code for the measurements when creating a ping.

We will have to modify each implementation to support two versions of the
measurements (whole-session and sub-session).
We might want to report only the whole-session version of these
measurements initially.

On Wed, Jan 28, 2015 at 3:28 PM, Vladan Djeric <vdjeric at mozilla.com> wrote:

> We're considering submitting both a full-session Telemetry/FHR ping and
> subsession pings during each Firefox session as a stopgap measure while we
> unify Telemetry & FHR.
>
> I volunteered to look into the memory overhead of this approach.
>
> In my Firefox 35 (release) session on Windows 7 with an uptime of 18
> hours, I noted the following entries for Telemetry in about:memory:
>
>    - 1MB TelemetryFile for single-process
>       - This is completely unexpected, I filed bug 1126986
>       <https://bugzilla.mozilla.org/show_bug.cgi?id=1126986>
>    - *270 kB for Telemetry heap data allocated by C++ code*
>       - *Pretty much all the Telemetry data (histograms and other data
>       types) are stored in C++ code*
>       - 106 kB for TelemetryPing.jsm
>    - 74 kB for BrowserUITelemetry.jsm
>    - 34 kB for TelemetryLog.jsm
>    - 34 kB for TelemetryStopwatch.jsm
>    - 29 kB for TelemetryTimestamps.jsm
>    - 27 kB for UITelemetry.jsm
>    - 23KB for TelemetryStartup.js
>
> The actual Telemetry ping for this session was 112 KB in uncompressed JSON
> form.
> An 8 day session from Nightly 38 (non-E10S) on Windows 8.1 had very
> similar numbers.
> Each process in an E10S session had roughly the same cost as the numbers
> above.
>
> I think an additional ~300KB memory overhead on desktop machines is
> acceptable.
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/fhr-dev/attachments/20150128/c7b95152/attachment.html>