Currently the available memory tracker will start sending memory-pressure/low-memory events once we hit 256MiB free commit space (on all Windows systems) or 256MiB free virtual memory (only on 32-bit Windows systems).

Crash ping data shows that ~1/3 of our OOM crashes happen before hitting these thresholds. After bug 675539 lands we should re-evalute the thresholds and tweak them to maximize its impact. There's no point in doing it before as unloading tabs might change fairly dramatically the profile of our OOM crashes.

After analyzing crash ping data we've established that the current low-memory
detection threshold is too low, there are still a fair number of crashes
happening above it. A 50% increase to 384 MiB should be just about right in
the light of recent telemetry data.

https://hg.mozilla.org/mozilla-central/rev/09479d92114b

Comment on attachment 9051622 [details]
Bug 1529556 - Increase the low-memory detection thresholds by 50%

Beta/Release Uplift Approval Request

• Feature/Bug causing the regression: Bug 675539
• User impact if declined: Tab unloading is not as effective as it could be in avoiding an OOM crash
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): This tweaks two parameters used by the available memory tracker on Windows to detect low-memory scenarios. Increasing those threshold values should help us detect low-memory scenarios more effectively: the original thresholds were based on the nightly population but on beta there's many more OOM crashes coming from 32-bit Windows machines running out of virtual space, the tweaked thresholds should cover better the beta population (and hopefully the release population too). This has been in nightly for a while w/o causing regressions.
• String changes made/needed: None

Comment on attachment 9051622 [details]
Bug 1529556 - Increase the low-memory detection thresholds by 50%

Looks low risk and should improve our OOM crash rate, uplift approved for 67 beta 10, thanks.

https://hg.mozilla.org/releases/mozilla-beta/rev/ac8fd50744de