]> Cypherpunks repositories - gostls13.git/commit
net/http: reduce memory usage when hijacking
authorJakob Ackermann <das7pad@outlook.com>
Mon, 3 Mar 2025 22:16:38 +0000 (22:16 +0000)
committerGopher Robot <gobot@golang.org>
Wed, 9 Apr 2025 20:49:52 +0000 (13:49 -0700)
commitcfb78d63bd1e9a13e58920f7670da7b807b29a0d
tree4ef9e9fe2c7c309e3e4ec2e17b6cc035195162d2
parentcac276f81a5ff11ae3c9027c45d14469f2b7fb70
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)

Change-Id: I20a37ee314ed0d47463a4657d712154e78e48138
GitHub-Last-Rev: 80f09dfa273035f53cdd72845e5c5fb129c3e230
GitHub-Pull-Request: golang/go#70756
Reviewed-on: https://go-review.googlesource.com/c/go/+/634855
Reviewed-by: Sean Liao <sean@liao.dev>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Sean Liao <sean@liao.dev>
src/net/http/serve_test.go
src/net/http/server.go