Closed Bug 1543407 Opened 2 years ago Closed 5 months ago

Profiler uses more ~50% memory than indicated in the 'buffersize' setting in the UI


(Core :: Gecko Profiler, defect, P3)

52 Branch



Fission Milestone Future


(Reporter: jesup, Unassigned)


(Blocks 2 open bugs)


(Whiteboard: [MemShrink:P3])

With a buffersize in the UI of 90MB, I see in about:memory that profiler-state for every process (including GPU...) is 144MB (Windows 10, x64).

Note also that using this much memory per-process will be a problem in Fission; it's already a problem on a low-memory machine like the 2017 reference laptop with 4GB - 4 tabs open, almost no browsing (3 are profiles), and we have 9 processes * 144MB just for profiler state.

Fission Milestone: --- → ?
Priority: -- → P3

The 90MB from the UI are calculated as 9 bytes per entry * 10000000 entries. However, when requesting 10000000 entries, the ProfileBuffer constructor rounds it up to the next power of two, which is 16777216. So we request an allocation of 16777216 * 9 = 150994944 bytes, which is 144MiB.

We could fix this by making the UI snap to entry counts which are powers of two.

So this would be a bug for ?
Also I think the UI isn't clear that the memory amount is per process (or even per thread?).

Whiteboard: [memshrink] → [MemShrink:P3]
Fission Milestone: ? → Future

Fixed by bug 1634216 and bug 1634234: about:profiling now shows the exact power of 2 in bytes that the profiler will use.

Also, thanks to bug 1632750 this limit is now for the whole Firefox application, instead of a local limit in each process.

Closed: 5 months ago
Depends on: 1634216, 1634234, 1632750
Resolution: --- → FIXED
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