IndexHard4-4 1.50ms ± 2% 0.71ms ± 0% -52.36% (p=0.000 n=20+19)
This also fixes a bug, that caused a string of length 16 to use
two 8-byte comparisons instead of one 16-byte. And adds a test for
cases when partial_match fails.
Change-Id: I1ee8fc4e068bb36c95c45de78f067c822c0d9df0
Reviewed-on: https://go-review.googlesource.com/22551
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Redo of CL 28575 with fixed test.
We're in a pre-KeepAlive world for a bit yet, the old tests
were in a client which was in a post-KeepAlive world.
Change-Id: I114fd630339d761ab3306d1d99718d3cb973678d
Reviewed-on: https://go-review.googlesource.com/28582
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This has always been the case but it was not obvious from the documentation.
The reason for the quoting is that String() may return an abbreviated string,
starting with double-quote (") but ending in ... (w/o a quote). The missing
quote indicates the abbreviation (in contrast to a string ending in ...").
constant.StringVal can be used to obtain the unquoted string of a String Value.
Change-Id: Id0ba45b6ff62b3e024386ba8d907d6b3a4fcb6d7
Reviewed-on: https://go-review.googlesource.com/28576
Reviewed-by: Alan Donovan <adonovan@google.com>
Reason for revert: broke the build due to cherrypick;
relies on an unsubmitted parent CL.
Original issue's description:
> cmd/compile: ignore contentEscapes for marking nodes as escaping
>
> We can still stack allocate and VarKill nodes which don't
> escape but their content does.
>
> Fixes#16996
>
> Change-Id: If8aa0fcf2c327b4cb880a3d5af8d213289e6f6bf
> Reviewed-on: https://go-review.googlesource.com/28575
> Run-TryBot: Keith Randall <khr@golang.org>
> TryBot-Result: Gobot Gobot <gobot@golang.org>
> Reviewed-by: David Chase <drchase@google.com>
>
Change-Id: Ie1a325209de14d70af6acb2d78269b7a0450da7a
Reviewed-on: https://go-review.googlesource.com/28578
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
We can still stack allocate and VarKill nodes which don't
escape but their content does.
Fixes#16996
Change-Id: If8aa0fcf2c327b4cb880a3d5af8d213289e6f6bf
Reviewed-on: https://go-review.googlesource.com/28575
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Includes test case shown to fail with unpatched compiler.
Fixes#17005.
Change-Id: I49b7b1a3f02736d85846a2588018b73f68d50320
Reviewed-on: https://go-review.googlesource.com/28573
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
When the divisor is known to be a constant
non-zero, don't insert panicdivide calls
that will just be eliminated later.
The main benefit here is readability of the SSA
form for compiler developers.
Change-Id: Icb7d07fc996941fbaff84524ac3e4b53d8e75fda
Reviewed-on: https://go-review.googlesource.com/28530
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
TestFreeOSMemory was disabled on many arches because of issue #9993.
Since that's been fixed, enable the test everywhere.
Change-Id: I298c38c3e04128d9c8a1f558980939d5699bea03
Reviewed-on: https://go-review.googlesource.com/27403
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
syscall.Getpagesize currently returns hard-coded page sizes on all
architectures (some of which are probably always wrong, and some of
which are definitely not always right). The runtime now has this
information, queried from the OS during runtime init, so make
syscall.Getpagesize return the page size that the runtime knows.
Updates #10180.
Change-Id: I4daa6fbc61a2193eb8fa9e7878960971205ac346
Reviewed-on: https://go-review.googlesource.com/25051
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Now that the runtime fetches the true physical page size from the OS,
make the physical page size used by heap growth a variable instead of
a constant. This isn't used in any performance-critical paths, so it
shouldn't be an issue.
sys.PhysPageSize is also renamed to sys.DefaultPhysPageSize to make it
clear that it's not necessarily the true page size. There are no uses
of this constant any more, but we'll keep it around for now.
Updates #12480 and #10180.
Change-Id: I6c23b9df860db309c38c8287a703c53817754f03
Reviewed-on: https://go-review.googlesource.com/25022
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently the physical page size assumed by the runtime is hard-coded.
On Linux the runtime at least fetches the OS page size during init and
sanity checks against the hard-coded value, but they may still differ.
On other OSes we wouldn't even notice.
Add support on all OSes to fetch the actual OS physical page size
during runtime init and lift the sanity check of PhysPageSize from the
Linux init code to general malloc init. Currently this is the only use
of the retrieved page size, but we'll add more shortly.
Updates #12480 and #10180.
Change-Id: I065f2834bc97c71d3208edc17fd990ec9058b6da
Reviewed-on: https://go-review.googlesource.com/25050
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently we assume the physical page size on ARM is 4kB. While this
is usually true, the architecture also supports 16kB and 64kB physical
pages, and Linux (and possibly other OSes) can be configured to use
these larger page sizes.
With Go 1.6, such a configuration could potentially run, but generally
resulted in memory corruption or random panics. With current master,
this configuration will cause the runtime to panic during init on
Linux when it checks the true physical page size (and will still cause
corruption or panics on other OSes).
However, the assumed physical page size only has to be a multiple of
the true physical page size, the scavenger can now deal with large
physical page sizes, and the rest of the runtime can deal with a
larger assumed physical page size than the true size. Hence, there's
little disadvantage to conservatively setting the assumed physical
page size to 64kB on ARM.
This may result in some extra memory use, since we can only return
memory at multiples of the assumed physical page size. However, it is
a simple change that should make Go run on systems configured for
larger page sizes. The following commits will make the runtime query
the actual physical page size from the OS, but this is a simple step
there.
Updates #12480.
Change-Id: I851829595bc9e0c76235c847a7b5f62ad82b5302
Reviewed-on: https://go-review.googlesource.com/25021
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
Currently the time spent in scanobject is proportional to the size of
the object being scanned. Since scanobject is non-preemptible, large
objects can cause significant goroutine (and even whole application)
delays through several means:
1. If a GC assist picks up a large object, the allocating goroutine is
blocked for the whole scan, even if that scan well exceeds that
goroutine's debt.
2. Since the scheduler does not run on the P performing a large object
scan, goroutines in that P's run queue do not run unless they are
stolen by another P (which can take some time). If there are a few
large objects, all of the Ps may get tied up so the scheduler
doesn't run anywhere.
3. Even if a large object is scanned by a background worker and other
Ps are still running the scheduler, the large object scan doesn't
flush background credit until the whole scan is done. This can
easily cause all allocations to block in assists, waiting for
credit, causing an effective STW.
Fix this by splitting large objects into 128 KB "oblets" and scanning
at most one oblet at a time. Since we can scan 1–2 MB/ms, this equates
to bounding scanobject at roughly 100 µs. This improves assist
behavior both because assists can no longer get "unlucky" and be stuck
scanning a large object, and because it causes the background worker
to flush credit and unblock assists more frequently when scanning
large objects. This also improves GC parallelism if the heap consists
primarily of a small number of very large objects by letting multiple
workers scan a large objects in parallel.
Fixes#10345. Fixes#16293.
This substantially improves goroutine latency in the benchmark from
issue #16293, which exercises several forms of very large objects:
name old max-latency new max-latency delta
SliceNoPointer-12 154µs ± 1% 155µs ± 2% ~ (p=0.087 n=13+12)
SlicePointer-12 314ms ± 1% 5.94ms ±138% -98.11% (p=0.000 n=19+20)
SliceLivePointer-12 1148ms ± 0% 4.72ms ±167% -99.59% (p=0.000 n=19+20)
MapNoPointer-12 72509µs ± 1% 408µs ±325% -99.44% (p=0.000 n=19+18)
ChanPointer-12 313ms ± 0% 4.74ms ±140% -98.49% (p=0.000 n=18+20)
ChanLivePointer-12 1147ms ± 0% 3.30ms ±149% -99.71% (p=0.000 n=19+20)
name old P99.9-latency new P99.9-latency delta
SliceNoPointer-12 113µs ±25% 107µs ±12% ~ (p=0.153 n=20+18)
SlicePointer-12 309450µs ± 0% 133µs ±23% -99.96% (p=0.000 n=20+20)
SliceLivePointer-12 961ms ± 0% 1.35ms ±27% -99.86% (p=0.000 n=20+20)
MapNoPointer-12 448µs ±288% 119µs ±18% -73.34% (p=0.000 n=18+20)
ChanPointer-12 309450µs ± 0% 134µs ±23% -99.96% (p=0.000 n=20+19)
ChanLivePointer-12 961ms ± 0% 1.35ms ±27% -99.86% (p=0.000 n=20+20)
This has negligible effect on all metrics from the garbage, JSON, and
HTTP x/benchmarks.
It shows slight improvement on some of the go1 benchmarks,
particularly Revcomp, which uses some multi-megabyte buffers:
name old time/op new time/op delta
BinaryTree17-12 2.46s ± 1% 2.47s ± 1% +0.32% (p=0.012 n=20+20)
Fannkuch11-12 2.82s ± 0% 2.81s ± 0% -0.61% (p=0.000 n=17+20)
FmtFprintfEmpty-12 50.8ns ± 5% 50.5ns ± 2% ~ (p=0.197 n=17+19)
FmtFprintfString-12 131ns ± 1% 132ns ± 0% +0.57% (p=0.000 n=20+16)
FmtFprintfInt-12 117ns ± 0% 116ns ± 0% -0.47% (p=0.000 n=15+20)
FmtFprintfIntInt-12 180ns ± 0% 179ns ± 1% -0.78% (p=0.000 n=16+20)
FmtFprintfPrefixedInt-12 186ns ± 1% 185ns ± 1% -0.55% (p=0.000 n=19+20)
FmtFprintfFloat-12 263ns ± 1% 271ns ± 0% +2.84% (p=0.000 n=18+20)
FmtManyArgs-12 741ns ± 1% 742ns ± 1% ~ (p=0.190 n=19+19)
GobDecode-12 7.44ms ± 0% 7.35ms ± 1% -1.21% (p=0.000 n=20+20)
GobEncode-12 6.22ms ± 1% 6.21ms ± 1% ~ (p=0.336 n=20+19)
Gzip-12 220ms ± 1% 219ms ± 1% ~ (p=0.130 n=19+19)
Gunzip-12 37.9ms ± 0% 37.9ms ± 1% ~ (p=1.000 n=20+19)
HTTPClientServer-12 82.5µs ± 3% 82.6µs ± 3% ~ (p=0.776 n=20+19)
JSONEncode-12 16.4ms ± 1% 16.5ms ± 2% +0.49% (p=0.003 n=18+19)
JSONDecode-12 53.7ms ± 1% 54.1ms ± 1% +0.71% (p=0.000 n=19+18)
Mandelbrot200-12 4.19ms ± 1% 4.20ms ± 1% ~ (p=0.452 n=19+19)
GoParse-12 3.38ms ± 1% 3.37ms ± 1% ~ (p=0.123 n=19+19)
RegexpMatchEasy0_32-12 72.1ns ± 1% 71.8ns ± 1% ~ (p=0.397 n=19+17)
RegexpMatchEasy0_1K-12 242ns ± 0% 242ns ± 0% ~ (p=0.168 n=17+20)
RegexpMatchEasy1_32-12 72.1ns ± 1% 72.1ns ± 1% ~ (p=0.538 n=18+19)
RegexpMatchEasy1_1K-12 385ns ± 1% 384ns ± 1% ~ (p=0.388 n=20+20)
RegexpMatchMedium_32-12 112ns ± 1% 112ns ± 3% ~ (p=0.539 n=20+20)
RegexpMatchMedium_1K-12 34.4µs ± 2% 34.4µs ± 2% ~ (p=0.628 n=18+18)
RegexpMatchHard_32-12 1.80µs ± 1% 1.80µs ± 1% ~ (p=0.522 n=18+19)
RegexpMatchHard_1K-12 54.0µs ± 1% 54.1µs ± 1% ~ (p=0.647 n=20+19)
Revcomp-12 387ms ± 1% 369ms ± 5% -4.89% (p=0.000 n=17+19)
Template-12 62.3ms ± 1% 62.0ms ± 0% -0.48% (p=0.002 n=20+17)
TimeParse-12 314ns ± 1% 314ns ± 0% ~ (p=1.011 n=20+13)
TimeFormat-12 358ns ± 0% 354ns ± 0% -1.12% (p=0.000 n=17+20)
[Geo mean] 53.5µs 53.3µs -0.23%
Change-Id: I2a0a179d1d6bf7875dd054b7693dd12d2a340132
Reviewed-on: https://go-review.googlesource.com/23540
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Commit 59877bf renamed bitMarked to bitScan, since the bitmap is no
longer used for marking. However, there were several other references
to this strewn about comments and in some other constant names. Fix
these up, too.
Change-Id: I4183d28c6b01977f1d75a99ad55b150f2211772d
Reviewed-on: https://go-review.googlesource.com/28450
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Enabled checks (except for DUFF-ops which aren't implemented yet).
Added ppc64le to relevant test.
Also updated register list to reflect no-longer-reserved-
for-constants status (file was missed in that change).
Updates #16010.
Change-Id: I31b1aac19e14994f760f2ecd02edbeb1f78362e7
Reviewed-on: https://go-review.googlesource.com/28548
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This program is written in Go now.
Change-Id: Ieec21a1bcac7c7a59e88cd1e1359977659de1757
Reviewed-on: https://go-review.googlesource.com/28549
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
For each exported symbol in package main, add its name and type to
go.plugin.tabs symbol. This is used by the runtime when loading a
plugin to return a typed interface{} value.
Change-Id: I23c39583e57180acb8f7a74d218dae4368614f46
Reviewed-on: https://go-review.googlesource.com/27818
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
1.7 introduced a significant regression compared to 1.6:
SqrtIndirect-4 2.32ns ± 0% 7.86ns ± 0% +238.79% (p=0.000 n=20+18)
This is caused by sqrtsd preserving upper part of destination register.
Which introduces dependency on previous value of X0.
In 1.6 benchmark loop didn't use X0 immediately after call:
callq *%rbx
movsd 0x8(%rsp),%xmm2
movsd 0x20(%rsp),%xmm1
addsd %xmm2,%xmm1
mov 0x18(%rsp),%rax
inc %rax
jmp loop
In 1.7 however xmm0 is used just after call:
callq *%rbx
mov 0x10(%rsp),%rcx
lea 0x1(%rcx),%rax
movsd 0x8(%rsp),%xmm0
movsd 0x18(%rsp),%xmm1
I've verified that this is caused by dependency, by inserting
XORPS X0,X0 in the beginning of math.Sqrt, which puts performance back on 1.6 level.
Splitting SQRTSD mem,reg into:
MOVSD mem,reg
SQRTSD reg,reg
Removes dependency, because MOVSD (load version)
doesn't need to preserve upper part of a register.
And reg,reg operation is solved by renamer in CPU.
As a result of this change regression is gone:
SqrtIndirect-4 7.86ns ± 0% 2.33ns ± 0% -70.36% (p=0.000 n=18+17)
This also removes old Sqrt benchmarks, in favor of benchmarks measuring latency.
Only SqrtIndirect is kept, to show impact of this patch.
Change-Id: Ic7eebe8866445adff5bc38192fa8d64c9a6b8872
Reviewed-on: https://go-review.googlesource.com/28392
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
Reviewed-by: Keith Randall <khr@golang.org>
This should have happened as part of CL 28485.
Change-Id: I63cd31303e542ceaec3f4002c5573f186a1e9a52
Reviewed-on: https://go-review.googlesource.com/28547
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
It should alias to Xchg instead of Swap. Found when testing #16985.
Change-Id: If9fd734a1f89b8b2656f421eb31b9d1b0d95a49f
Reviewed-on: https://go-review.googlesource.com/28512
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
The previous if condition already checks the same expression and doesn't
have side effects.
Change-Id: Ieaf30a786572b608d0a883052b45fd3f04bc6147
Reviewed-on: https://go-review.googlesource.com/28475
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
No test because the language spec makes no promises in this area.
Fixes#16983
Change-Id: I1a6aa7ff87dd14aa27e8400040a6f6fc908aa1fd
Reviewed-on: https://go-review.googlesource.com/28533
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Use existing helper function instead of importing "net/http". This
allows the go_bootstrap build to not depend on "net/http" package.
See cmd/go/http.go for details.
Fixes build bootstrap build with all.bash.
Change-Id: I2fd0fb01af7774f1690a353af22137680ec78170
Reviewed-on: https://go-review.googlesource.com/28531
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This is a slightly rough, skeletal implementation.
We will polish and add to it through use.
.github/ISSUE_TEMPLATE will be updated in a
separate CL.
Fixes#16635
Change-Id: Icf284170d87e61b5b643366c85cffc48f149f730
Reviewed-on: https://go-review.googlesource.com/28485
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The ctxt parameter is always set to 0 on entry into anylit so make this
parameter a literal constant, and where possibly remove ctxt as a parameter
where it is known to be a constant zero.
Passes toolstash -cmp.
This is a re-creation of CL 28221 by Dave Cheney.
That CL was graciously reverted in CL 28480
to make merging other CLs easier.
Change-Id: If7a57bf0e27774d9890adbc30af9fabb4aff1058
Reviewed-on: https://go-review.googlesource.com/28483
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
They were almost identical.
Merge them and some of their calling code.
Passes toolstash -cmp.
Change-Id: I9e92a864a6c09c9e18ed52dc247a678467e344ba
Reviewed-on: https://go-review.googlesource.com/26754
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Does not pass toolstash -cmp due to changed export data,
but the cmd/go binary (which doesn't contain export data)
is bit-for-bit identical.
Change-Id: I6b12f9de18cf7da528e9207dccbf8f08c969f142
Reviewed-on: https://go-review.googlesource.com/26753
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reduce the duplication in every arch by moving the code into package gc.
Change-Id: Ia111add8316492571825431ecd4f0154c8792ae1
Reviewed-on: https://go-review.googlesource.com/28481
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
This custom version is identical to CheckLoweredPhi. The addition of
CheckLoweredPhi likely raced with adding PPC64.
Change-Id: I294dcb758d312e93fb8842f4d1e12bf0f63a1e06
Reviewed-on: https://go-review.googlesource.com/28479
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
It was fixed earlier in the Go 1.8 cycle.
Add a test.
Fixes#15895
Change-Id: I5834831235d99b9fcf21b435932cdd7ac6dc2c6e
Reviewed-on: https://go-review.googlesource.com/28476
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The ctxt parameter is always set to 0 on entry into anylit so make this
parameter a literal constant, and where possibly remove ctxt as a parameter
where it is known to be a constant zero.
Change-Id: I3e76e06456d7b1a1ea875ffeb2efefa4a1ff5a7e
Reviewed-on: https://go-review.googlesource.com/28221
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The http.Transport's retry can't retry requests with non-nil
bodies. When cloning an incoming server request into an outgoing
client request, nil out the Body field if the ContentLength is 0. (For
server requests, Body is always non-nil, even for GET, HEAD, etc.)
Also, don't use the deprecated CancelRequest and use Context instead.
And don't set Proto, ProtoMajor, ProtoMinor. Those are ignored in
client requests, which was probably a later documentation
clarification.
Fixes#16036
Updates #16696 (remove useless Proto lines)
Change-Id: I70a869e9bd4bf240c5838e82fb5aa695a539b343
Reviewed-on: https://go-review.googlesource.com/28412
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
