My current theory is that we need to run the arm pgo profile on an arm CPU to get the performance back. Talking to aklotz last month he mentioned that he believe that pgo profiles should be run on actual devices only, I'm gonna look into that, it might get us better perf on arm64 too (which is the large majority of our users)
Bug 1722266 Comment 5 Edit History
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My current theory is that we need to run the arm pgo profile on an arm CPU to get the performance back. Talking to aklotz last month he mentioned that he believes that pgo profiles should be run on actual devices only, I'm gonna look into that, it might get us better perf on arm64 too (which is the large majority of our users)