f18109d7e3
Currently, we map and grow the heap a whole arena (64MB) at a time. Unfortunately, in order to fix #32828, we need to switch from scavenging inline with allocation back to scavenging on heap growth, but heap-growth scavenging happens in large jumps because we grow the heap in large jumps. In order to prepare for better heap-growth scavenging, this CL separates mapping more space for the heap from actually "growing" it (tracking the new space with spans). Instead, growing the heap keeps track of the "current arena" it's growing into. It track that with new spans as needed, and only maps more arena space when the current arena is inadequate. The effect to the user is the same, but this will let us scavenge on much smaller increments of heap growth. There are two slightly subtleties to this change: 1. If an allocation requires mapping a new arena and that new arena isn't contiguous with the current arena, we don't want to lose the unused space in the current arena, so we have to immediately track that with a span. 2. The mapped space must be accounted as released and idle, even though it isn't actually tracked in a span. For #32828, since this makes heap-growth scavenging far more effective, especially at small heap sizes. For example, this change is necessary for TestPhysicalMemoryUtilization to pass once we remove inline scavenging. Change-Id: I300e74a0534062467e4ce91cdc3508e5ef9aa73a Reviewed-on: https://go-review.googlesource.com/c/go/+/189957 Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Michael Knyszek <mknyszek@google.com> |
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