c0392d2e7f
This splits the heap bitmap into separate chunks for every 64MB of the heap and introduces an index mapping from virtual address to metadata. It modifies the heapBits abstraction to use this two-level structure. Finally, it modifies heapBitsSetType to unroll the bitmap into the object itself and then copy it out if the bitmap would span discontiguous bitmap chunks. This is a step toward supporting general sparse heaps, which will eliminate address space conflict failures as well as the limit on the heap size. It's also advantageous for 32-bit. 32-bit already supports discontiguous heaps by always starting the arena at address 0. However, as a result, with a contiguous bitmap, if the kernel chooses a high address (near 2GB) for a heap mapping, the runtime is forced to map up to 128MB of heap bitmap. Now the runtime can map sections of the bitmap for just the parts of the address space used by the heap. Updates #10460. This slightly slows down the x/garbage and compilebench benchmarks. However, I think the slowdown is acceptably small. name old time/op new time/op delta Template 178ms ± 1% 180ms ± 1% +0.78% (p=0.029 n=10+10) Unicode 85.7ms ± 2% 86.5ms ± 2% ~ (p=0.089 n=10+10) GoTypes 594ms ± 0% 599ms ± 1% +0.70% (p=0.000 n=9+9) Compiler 2.86s ± 0% 2.87s ± 0% +0.40% (p=0.001 n=9+9) SSA 7.23s ± 2% 7.29s ± 2% +0.94% (p=0.029 n=10+10) Flate 116ms ± 1% 117ms ± 1% +0.99% (p=0.000 n=9+9) GoParser 146ms ± 1% 146ms ± 0% ~ (p=0.193 n=10+7) Reflect 399ms ± 0% 403ms ± 1% +0.89% (p=0.001 n=10+10) Tar 173ms ± 1% 174ms ± 1% +0.91% (p=0.013 n=10+9) XML 208ms ± 1% 210ms ± 1% +0.93% (p=0.000 n=10+10) [Geo mean] 368ms 371ms +0.79% name old time/op new time/op delta Garbage/benchmem-MB=64-12 2.17ms ± 1% 2.21ms ± 1% +2.15% (p=0.000 n=20+20) Change-Id: I037fd283221976f4f61249119d6b97b100bcbc66 Reviewed-on: https://go-review.googlesource.com/85883 Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Rick Hudson <rlh@golang.org> |
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