cfb78d63bd
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>
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