995165 - ARM v6 GC settings should be changed to prevent triggering a loop of multiple GCs.

Status: RESOLVED FIXED

(Core :: JavaScript: GC, defect)

Description

[Nicolas B. Pierron [:nbp — off until 29-09]]

The current GC settings which are used on low-memory Android (armv6 devices) [1] are damn to low and they are more likely to cause GC-loops.

The reason being that if all the heap is live, we would push the GC trigger by these multipliers, but the factor used to set the trigger is based on the quantity of live objects to which we apply a multiplier of 0.85 / 0.9 [2].  This trigger multiplier implies that:

javascript.options.mem.gc_low_frequency_heap_growth
    should be higher than 112 (> 1 / 0.9)

javascript.options.mem.gc_high_frequency_heap_growth_max &
javascript.options.mem.gc_high_frequency_heap_growth_min
    should be higher than 118 (> 1 / 0.85)

As we are changing these GC settings we should probably assert/warn about this issue.

[1] http://dxr.mozilla.org/mozilla-central/source/mobile/android/app/mobile.js?from=mobile.js#415,418
[2] http://dxr.mozilla.org/mozilla-central/source/js/src/jsgc.cpp#2247

Comment 1

[Nicolas B. Pierron [:nbp — off until 29-09]]

Attachment: Fix Armv6 GC settings

Comment 2

[Terrence Cole [:terrence]]

Comment on attachment 8405446 [details] [diff] [review]
Fix Armv6 GC settings

Review of attachment 8405446 [details] [diff] [review]:
-----------------------------------------------------------------

r=me Great catch!

Comment 3

[Nicolas B. Pierron [:nbp — off until 29-09]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/8869f945b355

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/8869f945b355

Comment 5

[Mark Finkle (:mfinkle) (use needinfo?)]

We don't need to track for fennec, but if you want to uplift ask for approval.