andrew grant 8168aa1717 Change UBT limiting of actions based on memory to use total ram on Mac instead of free ram. ...

This addresses issues with CPU resources on Mac going under utilized on systems where total RAM is only 2-3x the number of cores (e.g 8c/16GB, 10c/32GB) and the user has applications running (UE, XCode, browsers) that are occupying RAM.

Historically this check limited actions based on free memory to ensure action processes weren't forced to use swap, but there's strong evidence that limiting based on total system memory and relying on the OS to swap out other processes to make room is fine. That said only Mac has been extensively tested here in this scenario (and tends to have faster disk performance than other platforms). So for now we'll change Mac and leave Windows/Linux using the old behavior

Tests -

* Ran on an M1 8c/16GB Mac with Xcode & UE open and compared core utilization before (5) to after this change (8)
* Loaded up a bucket-load of apps, browser tabs, and a running game and verified engine built successfully 2x with no compiler OOMs

#jira UE-192238
#rb swarm
#swarm [at]Joe.Kirchoff [at]Zack.Neyland

[CL 26906094 by andrew grant in ue5-main branch]

2023-08-07 19:49:26 -04:00

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