[go] cmd/link: don't disable memory profiling when pprof.WriteHeapProfile is used

[Cherry Mui (Gerrit)]

Cherry Mui submitted the change

Change information

Commit message:

cmd/link: don't disable memory profiling when pprof.WriteHeapProfile is used

We have an optimization that if the memory profile is not consumed
anywhere, we set the memory profiling rate to 0 to disable the
"background" low-rate profiling. We detect whether the memory
profile is used by checking whether the runtime.MemProfile function
is reachable at link time. Previously, all APIs that access the
memory profile go through runtime.MemProfile. But the code was
refactored in CL 572396, and now the legacy entry point
WriteHeapProfile uses pprof_memProfileInternal without going
through runtime.MemProfile. In fact, even with the recommended
runtime/pprof.Profile API (pprof.Lookup or pprof.Profiles),
runtime.MemProfile is only (happen to be) reachable through
countHeap.

Change the linker to check runtime.memProfileInternal instead,
which is on all code paths that retrieve the memory profile. Add
a test case for WriteHeapProfile, so we cover all entry points.

Fixes #68136.

Change-Id: I075c8d45c95c81825a1822f032e23107aea4303c

Reviewed-on: https://go-review.googlesource.com/c/go/+/596538

Reviewed-by: Than McIntosh <th...@google.com>

LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Files:

• M src/cmd/link/internal/ld/ld_test.go
• M src/cmd/link/internal/ld/lib.go
• M src/runtime/mprof.go
• M src/runtime/pprof/pprof.go

Change size: S

Delta: 4 files changed, 41 insertions(+), 5 deletions(-)

Branch: refs/heads/master

Submit Requirements:

• Code-Review: +2 by Than McIntosh
• TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI

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Gerrit

Gerrit-MessageType: merged

Gerrit-Project: go

Gerrit-Branch: master

Gerrit-Change-Id: I075c8d45c95c81825a1822f032e23107aea4303c

Gerrit-Change-Number: 596538

Gerrit-PatchSet: 2

Gerrit-Owner: Cherry Mui <cher...@google.com>

Gerrit-Reviewer: Austin Clements <aus...@google.com>

Gerrit-Reviewer: Cherry Mui <cher...@google.com>

Gerrit-Reviewer: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Gerrit-Reviewer: Than McIntosh <th...@google.com>