Bug 201139 – run-webkit-tests: Cap the number of automatically booted simulators at 12

• Component: Tools / Tests
• Status: RESOLVED FIXED

[Jonathan Bedard]

It seems that with a larger number of cores and memory, simulators start to be bound by some other system resource. In particular, contributors with iMac Pros and 128 GB of RAM will boot between 16 and 20 simulators, and begin to see diminishing returns on how fast simulator tests are run. By default, we should cap the number of simulators we automatically boot at 12. Note that this change will not have an effect on the number of simulators booted unless a machine is automatically booting more than 12 simulators.

[Jonathan Bedard]

Created attachment 377245 [details]
Patch

[Jonathan Bedard]

In particular, some testing a year or two back indicated that RAM was usually the bottleneck when booting simulators, and 128 GB of RAM could boot up to 21 simulators...if you have that much RAM, CPU will usually be considered the bottleneck, which would leave you with 18, in most cases. Getting some feedback from different folks, it seems like this is rarely desired.

[Aakash Jain]

Comment on attachment 377245 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=377245&action=review

> Tools/Scripts/webkitpy/xcode/simulated_device.py:422
> +        max_supported_simulators_for_hardware = min(host.executive.cpu_count() // 2, host.platform.total_bytes_memory() // SimulatedDeviceManager.MEMORY_ESTIMATE_PER_SIMULATOR_INSTANCE, 12)

Please store 12 in a separate variable, something like MAX_NUMBER_OF_SIMULATORS.

[Jonathan Bedard]

Created attachment 377246 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 377246 [details]
Patch

Clearing flags on attachment: 377246

Committed r249102: <https://trac.webkit.org/changeset/249102>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/54711790>