| commit | 44078a32288ee8890882cb1578160715324407ff | [log] [tgz] |
|---|---|---|
| author | Austin Clements <austin@google.com> | Wed Sep 30 11:52:54 2015 -0400 |
| committer | Austin Clements <austin@google.com> | Fri Oct 02 20:20:43 2015 +0000 |
| tree | f63d60a5ad748507eaef02e31bee5632188d725b | |
| parent | 9a31d38f65354567719a31414ebcb31f0337b803 [diff] |
runtime: adjust huge page flags only on huge page granularity This fixes an issue where the runtime panics with "out of memory" or "cannot allocate memory" even though there's ample memory by reducing the number of memory mappings created by the memory allocator. Commit 7e1b61c worked around issue #8832 where Linux's transparent huge page support could dramatically increase the RSS of a Go process by setting the MADV_NOHUGEPAGE flag on any regions of pages released to the OS with MADV_DONTNEED. This had the side effect of also increasing the number of VMAs (memory mappings) in a Go address space because a separate VMA is needed for every region of the virtual address space with different flags. Unfortunately, by default, Linux limits the number of VMAs in an address space to 65530, and a large heap can quickly reach this limit when the runtime starts scavenging memory. This commit dramatically reduces the number of VMAs. It does this primarily by only adjusting the huge page flag at huge page granularity. With this change, on amd64, even a pessimal heap that alternates between MADV_NOHUGEPAGE and MADV_HUGEPAGE must reach 128GB to reach the VMA limit. Because of this rounding to huge page granularity, this change is also careful to leave large used and unused regions huge page-enabled. This change reduces the maximum number of VMAs during the runtime benchmarks with GODEBUG=scavenge=1 from 692 to 49. Fixes #12233. Change-Id: Ic397776d042f20d53783a1cacf122e2e2db00584 Reviewed-on: https://go-review.googlesource.com/15191 Reviewed-by: Keith Randall <khr@golang.org>
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