The Go programming language
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Jakob Ackermann 80f09dfa27
net/http: reduce memory usage when hijacking
Previously, Hijack allocated a new write buffer and the existing
connection write buffer used an extra 4KiB of memory until the handler
finished and the "conn" was garbage collected. Now, hijack re-uses the
existing write buffer and re-attaches it to the raw connection to avoid
referencing the net/http "conn" after returning.

After a handler that hijacked exited, the "conn" reference in
"connReader" will now be unset. This allows all of the "conn",
"response" and "Request" to get garbage collected.
Overall, this is reducing the memory usage by 43% or 6.7KiB per hijacked
connection (see BenchmarkServerHijackMemoryUsage in an earlier revision
of the CL).

CloseNotify will continue to work _before_ the handler has exited
(i.e. while the "conn" is still referenced in "connReader"). This aligns
with the documentation of CloseNotifier:
> After the Handler has returned, there is no guarantee that the channel
> receives a value.

goos: linux
goarch: amd64
pkg: net/http
cpu: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
               │   before    │             after              │
               │   sec/op    │    sec/op     vs base          │
ServerHijack-8   42.59µ ± 8%   39.47µ ± 16%  ~ (p=0.481 n=10)

               │    before    │                after                 │
               │     B/op     │     B/op      vs base                │
ServerHijack-8   16.12Ki ± 0%   12.06Ki ± 0%  -25.16% (p=0.000 n=10)

               │   before   │               after               │
               │ allocs/op  │ allocs/op   vs base               │
ServerHijack-8   51.00 ± 0%   49.00 ± 0%  -3.92% (p=0.000 n=10)
2025-03-03 23:08:29 +01:00
.github .github: update language change proposal template 2024-08-08 19:02:29 +00:00
api go/parser: deprecate parser.ParseDir 2025-02-19 11:49:13 -08:00
doc crypto/tls: require EMS in FIPS 140-3 mode 2025-02-25 11:50:05 -08:00
lib lib/time: build with Ubuntu backward compatibility options 2025-02-06 17:10:15 -08:00
misc misc/wasm: move wasm runtime files to lib/wasm 2024-08-30 19:15:21 +00:00
src net/http: reduce memory usage when hijacking 2025-03-03 23:08:29 +01:00
test cmd/compile: simplify intrinsification of TrailingZeros16 and TrailingZeros8 2025-02-27 03:45:44 -08:00
.gitattributes
.gitignore runtime,internal: move runtime/internal/sys to internal/runtime/sys 2024-07-23 19:05:35 +00:00
CONTRIBUTING.md
LICENSE LICENSE: update per Google Legal 2024-08-09 14:54:31 +00:00
PATENTS
README.md README: fix CC BY license name 2024-07-22 17:45:27 +00:00
SECURITY.md SECURITY.md: update the Reporting a Vulnerability link 2023-09-22 21:17:24 +00:00
codereview.cfg
go.env cmd/go: additional doc-inspired tests and bug fixes 2023-06-06 19:18:46 +00:00

README.md

The Go Programming Language

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

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