9d78e75a0a
This change adds a new inUse field to the allocator which tracks ranges of addresses that are owned by the heap. It is updated on each heap growth. These ranges are tracked in an array which is kept sorted. In practice this array shouldn't exceed its initial allocation except in rare cases and thus should be small (ideally exactly 1 element in size). In a hypothetical worst-case scenario wherein we have a 1 TiB heap and 4 MiB arenas (note that the address ranges will never be at a smaller granularity than an arena, since arenas are always allocated contiguously), inUse would use at most 4 MiB of memory if the heap mappings were completely discontiguous (highly unlikely) with an additional 2 MiB leaked from previous allocations. Furthermore, the copies that are done to keep the inUse array sorted will copy at most 4 MiB of memory in such a scenario, which, assuming a conservative copying rate of 5 GiB/s, amounts to about 800µs. However, note that in practice: 1) Most 64-bit platforms have 64 MiB arenas. 2) The copies should incur little-to-no page faults, meaning a copy rate closer to 25-50 GiB/s is expected. 3) Go heaps are almost always mostly contiguous. Updates #35514. Change-Id: I3ad07f1c2b5b9340acf59ecc3b9ae09e884814fe Reviewed-on: https://go-review.googlesource.com/c/go/+/207757 Run-TryBot: Michael Knyszek <mknyszek@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com> Reviewed-by: Austin Clements <austin@google.com> |
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