1. 07 Dec, 2019 2 commits
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  4. 04 Dec, 2019 7 commits
  5. 03 Dec, 2019 1 commit
    • Michael Anthony Knyszek's avatar
      runtime: convert page allocator bitmap to sparse array · acf3ff2e
      Michael Anthony Knyszek authored
      Currently the page allocator bitmap is implemented as a single giant
      memory mapping which is reserved at init time and committed as needed.
      This causes problems on systems that don't handle large uncommitted
      mappings well, or institute low virtual address space defaults as a
      memory limiting mechanism.
      
      This change modifies the implementation of the page allocator bitmap
      away from a directly-mapped set of bytes to a sparse array in same vein
      as mheap.arenas. This will hurt performance a little but the biggest
      gains are from the lockless allocation possible with the page allocator,
      so the impact of this extra layer of indirection should be minimal.
      
      In fact, this is exactly what we see:
          https://perf.golang.org/search?q=upload:20191125.5
      
      This reduces the amount of mapped (PROT_NONE) memory needed on systems
      with 48-bit address spaces to ~600 MiB down from almost 9 GiB. The bulk
      of this remaining memory is used by the summaries.
      
      Go processes with 32-bit address spaces now always commit to 128 KiB of
      memory for the bitmap. Previously it would only commit the pages in the
      bitmap which represented the range of addresses (lowest address to
      highest address, even if there are unused regions in that range) used by
      the heap.
      
      Updates #35568.
      Updates #35451.
      
      Change-Id: I0ff10380156568642b80c366001eefd0a4e6c762
      Reviewed-on: https://go-review.googlesource.com/c/go/+/207497
      Run-TryBot: Michael Knyszek <mknyszek@google.com>
      TryBot-Result: Gobot Gobot <gobot@golang.org>
      Reviewed-by: default avatarAustin Clements <austin@google.com>
      Reviewed-by: default avatarCherry Zhang <cherryyz@google.com>
      acf3ff2e