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Austin Clements d4a3466519 runtime: write trace stack tab directly to trace buffer
Currently, the stack frame of (*traceStackTable).dump is 68KiB. We're
about to move (*traceStackTable).dump to the system stack, where we
often don't have this much room.

5140 bytes of this is an on-stack temporary buffer for constructing
potentially large trace events before copying these out to the actual
trace buffer.

Reduce the stack frame size by writing these events directly to the
trace buffer rather than temporary space. This introduces a couple
complications:

- The trace event starts with a varint encoding the event payload's
  length in bytes. These events are large and somewhat complicated, so
  it's hard to know the size ahead of time. That's not a problem with
  the temporary buffer because we can just construct the event and see
  how long it is. In order to support writing directly to the trace
  buffer, we reserve enough bytes for a maximum size varint and add
  support for populating a reserved space after the fact.

- Emitting a stack event calls traceFrameForPC, which can itself emit
  string events. If these were emitted in the middle of the stack
  event, it would corrupt the stream. We already allocate a []Frame to
  convert the PC slice to frames, and then convert each Frame into a
  traceFrame with trace string IDs, so we address this by combining
  these two steps into one so that all trace string events are emitted
  before we start constructing the stack event.

For #53979.

Change-Id: Ie60704be95199559c426b551f8e119b14e06ddac
Reviewed-on: https://go-review.googlesource.com/c/go/+/422954
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
2022-08-11 20:16:29 +00:00
.github .github: remove duplicate security link 2022-01-07 17:55:09 +00:00
api debug/elf: add new-style LoongArch reloc types 2022-08-11 19:32:40 +00:00
doc doc: move Go 1.19 release notes to x/website 2022-08-01 18:07:12 +00:00
lib/time lib/time, time/tzdata: update to 2022b 2022-08-11 20:03:19 +00:00
misc misc/cgo/testsanitizers: fix code to detect gcc version correctly 2022-08-11 17:23:33 +00:00
src runtime: write trace stack tab directly to trace buffer 2022-08-11 20:16:29 +00:00
test test: make issue54343.go robust against the tiny allocator 2022-08-11 20:13:07 +00:00
.gitattributes all: treat all files as binary, but check in .bat with CRLF 2020-06-08 15:31:43 +00:00
.gitignore internal/buildcfg: move build configuration out of cmd/internal/objabi 2021-04-16 19:20:53 +00:00
codereview.cfg codereview.cfg: add codereview.cfg for master branch 2021-02-19 18:44:53 +00:00
CONTRIBUTING.md all: restore changes from faulty merge/revert 2018-02-12 20:13:59 +00:00
LICENSE
PATENTS
README.md README.md: update wiki link 2022-04-26 16:21:18 +00:00
SECURITY.md SECURITY.md: replace golang.org with go.dev 2022-04-26 19:59:47 +00:00

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