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runtime: don't eagerly collapse hugepages

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This has caused performance issues in production environments.

Disable it until further notice.

Fixes #63334.
Related to #61718 and #59960.

Change-Id: If84c5a8685825d43c912a71418f2597e44e867e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/531816
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
Michael Anthony Knyszek 2023-09-29 19:16:38 +00:00 committed by Gopher Robot
parent 0362f5ba14
commit 595deec3dd
1 changed files with 5 additions and 15 deletions
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20
src/runtime/mgcscavenge.go
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@ -1145,21 +1145,11 @@ func (s *scavengeIndex) alloc(ci chunkIdx, npages uint) {
// Mark that we're considering this chunk as backed by huge pages.
sc.setHugePage()
// Collapse dense chunks into huge pages and mark that
// we did that, but only if we're not allocating to
// use the entire chunk. If we're allocating an entire chunk,
// this is likely part of a much bigger allocation. For
// instance, if the caller is allocating a 1 GiB slice of bytes, we
// don't want to go and manually collapse all those pages; we want
// them to be demand-paged. If the caller is actually going to use
// all that memory, it'll naturally get backed by huge pages later.
//
// This also avoids having sysHugePageCollapse fail. On Linux,
// the call requires that some part of the huge page being collapsed
// is already paged in.
if !s.test && npages < pallocChunkPages {
sysHugePageCollapse(unsafe.Pointer(chunkBase(ci)), pallocChunkBytes)
}
// TODO(mknyszek): Consider eagerly backing memory with huge pages
// here. In the past we've attempted to use sysHugePageCollapse
// (which uses MADV_COLLAPSE on Linux, and is unsupported elswhere)
// for this purpose, but that caused performance issues in production
// environments.
}
s.chunks[ci].store(sc)
}