runtime: make the span allocation purpose more explicit

This change modifies mheap's span allocation API to have each caller
declare a purpose, defined as a new enum called spanAllocType.

The purpose behind this change is two-fold:
1. Tight control over who gets to allocate heap memory is, generally
   speaking, a good thing. Every codepath that allocates heap memory
   places additional implicit restrictions on the allocator. A notable
   example of a restriction is work bufs coming from heap memory: write
   barriers are not allowed in allocation paths because then we could
   have a situation where the allocator calls into the allocator.
2. Memory statistic updating is explicit. Instead of passing an opaque
   pointer for statistic updating, which places restrictions on how that
   statistic may be updated, we use the spanAllocType to determine which
   statistic to update and how.

We also take this opportunity to group all the statistic updating code
together, which should make the accounting code a little easier to
follow.

Change-Id: Ic0b0898959ba2a776f67122f0e36c9d7d60e3085
Reviewed-on: https://go-review.googlesource.com/c/go/+/246970
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
4 files changed
tree: ded07c5efca6a2266a8a033d715282a3705f796d
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. AUTHORS
  11. CONTRIBUTING.md
  12. CONTRIBUTORS
  13. favicon.ico
  14. LICENSE
  15. PATENTS
  16. README.md
  17. robots.txt
  18. SECURITY.md
README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

Gopher image Gopher image by Renee French, licensed under Creative Commons 3.0 Attributions license.

Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.

Download and Install

Binary Distributions

Official binary distributions are available at https://golang.org/dl/.

After downloading a binary release, visit https://golang.org/doc/install or load doc/install.html in your web browser for installation instructions.

Install From Source

If a binary distribution is not available for your combination of operating system and architecture, visit https://golang.org/doc/install/source or load doc/install-source.html in your web browser for source installation instructions.

Contributing

Go is the work of thousands of contributors. We appreciate your help!

To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html

Note that the Go project uses the issue tracker for bug reports and proposals only. See https://golang.org/wiki/Questions for a list of places to ask questions about the Go language.