d4bf716793
There are two additional sources of memory overhead per P that come from greenteagc. One is for ptrBuf, but on platforms other than Windows it doesn't actually cost anything due to demand-paging (Windows also demand-pages, but the memory is 'committed' so it still counts against OS RSS metrics). The other is for per-sizeclass scan stats. However when greenteagc is disabled, most of these scan stats are completely unused. The worst-case memory overhead from these two sources is relatively small (about 10 KiB per P), but for programs with a small memory footprint running on a machine with a lot of cores, this can be significant (single-digit percent). This change does two things. First, it puts ptrBuf initialization behind the greenteagc experiment, so now that memory is never allocated by default. Second, it abstracts the implementation details of scan stat collection and emission, such that we can have two different implementations depending on the build tag. This lets us remove all the unused stats when the greenteagc experiment is disabled, reducing the memory overhead of the stats from ~2.6 KiB per P to 536 bytes per P. This is enough to make the difference no longer noticable in our benchmark suite. Fixes #73931. Change-Id: I4351f1cbb3f6743d8f5922d757d73442c6d6ad3f Reviewed-on: https://go-review.googlesource.com/c/go/+/678535 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Michael Pratt <mpratt@google.com> |
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README.md
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