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24763 Commits

Author SHA1 Message Date
Russ Cox
28fb0d8023 cmd/go: fix addition of "math" dependency for arm binaries
p.ImportPath is the directory-derived path (like cmd/go).
p.Name is the actual package name.

Fixes #12089.

Change-Id: Ief76d42a85f811b0dfe2218affb48551527a7d44
Reviewed-on: https://go-review.googlesource.com/13530
Reviewed-by: David Crawshaw <crawshaw@golang.org>
2015-08-11 19:13:12 +00:00
Russ Cox
8ce80ce87d cmd/link: make -a output not crash
Fixes #12107.

Change-Id: I62f1b6ac9fb6f2cfa3472253dc1c6f7b7d2a6faf
Reviewed-on: https://go-review.googlesource.com/13448
Reviewed-by: David Crawshaw <crawshaw@golang.org>
2015-08-11 19:12:59 +00:00
David Symonds
1052b43213 net/mail: fix build.
Change-Id: I8f5c72c6c0db015c06d564523bab35d97d934578
Reviewed-on: https://go-review.googlesource.com/13510
Reviewed-by: Michael McGreevy <mcgreevy@golang.org>
Reviewed-by: David Symonds <dsymonds@golang.org>
2015-08-11 06:42:12 +00:00
David Symonds
1d75b40de8 net/mail: avoid panic in (*Address).String for malformed addresses.
Fixes #12098.

Change-Id: I190586484cd34856dccfafaba60eff0197c7dc20
Reviewed-on: https://go-review.googlesource.com/13500
Reviewed-by: Rob Pike <r@golang.org>
2015-08-11 05:07:30 +00:00
Rob Pike
546836556d cmd/yacc: use %q to print strings in Toknames
Fixes #12086

Belongs in 1.5

There remains a question of why the Statenames table's elements
are not printed. What purpose does that serve?

Change-Id: I83fd57b81d5e5065c3397a66ed457fc0d1c041bd
Reviewed-on: https://go-review.googlesource.com/13462
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2015-08-11 00:26:05 +00:00
Andrew Gerrand
8389e7cfa9 doc: link to Go 1.5 release notes from "project" page
Update issue #12102.

Change-Id: I9cafb284a848cc053bc7e5479c53ebf889b6d4d9
Reviewed-on: https://go-review.googlesource.com/13480
Reviewed-by: Rob Pike <r@golang.org>
2015-08-11 00:02:29 +00:00
Rob Pike
fe3d8d4db0 fmt: don't unread eof scanning %x
When scanning a hex byte at EOF, the code was ungetting the eof,
which backed up the input and caused double-scanning of a byte.

Delete the call to UnreadRune.

This line appeared in 1.5 for some reason; it was not in 1.4 and
should be removed again for 1.5

Fixes #12090.

Change-Id: Iad1ce8e7db8ec26615c5271310f4b0228cca7d78
Reviewed-on: https://go-review.googlesource.com/13461
Reviewed-by: Andrew Gerrand <adg@golang.org>
2015-08-10 03:34:48 +00:00
Dave Cheney
e7f4df7332 doc: NaCl requires pepper 41
Fixes #12062
Updates #11961

The sRPC nameservice was removed in pepper 42. For Go 1.5 stipulate
that NaCl requires pepper 41 only.

Change-Id: Ic88ba342d41f673391efaa96fb581712fa10a0fd
Reviewed-on: https://go-review.googlesource.com/13341
Reviewed-by: Andrew Gerrand <adg@golang.org>
2015-08-10 02:15:29 +00:00
Russ Cox
3ae17043f7 runtime: make sure heapBitsBulkBarrier cannot be preempted
Changes the torture test in #12068 from failing about 1/10 times
to not failing in almost 2,000 runs.

This was only happening in -race mode because functions are
bigger in -race mode, so a few of the helpers for heapBitsBulkBarrier
were not being inlined, and they were not marked nosplit,
so (only in -race mode) the write barrier was being preempted by GC,
causing missed pointer updates.

Filed issue #12069 for diagnosis of any other similar errors.

Fixes #12068.

Change-Id: Ic174d9b050ba278b18b08ab0d85a73c33bd5b175
Reviewed-on: https://go-review.googlesource.com/13364
Reviewed-by: Austin Clements <austin@google.com>
2015-08-07 17:55:26 +00:00
Russ Cox
4a19081358 runtime: run on GOARM=5 and GOARM=6 uniprocessor freebsd/arm systems
Also, crash early on non-Linux SMP ARM systems when GOARM < 7;
without the proper synchronization, SMP cannot work.

Linux is okay because we call kernel-provided routines for
synchronization and barriers, and the kernel takes care of
providing the right routines for the current system.
On non-Linux systems we are left to fend for ourselves.

It is possible to use different synchronization on GOARM=6,
but it's too late to do that in the Go 1.5 cycle.
We don't believe there are any non-Linux SMP GOARM=6 systems anyway.

Fixes #12067.

Change-Id: I771a556e47893ed540ec2cd33d23c06720157ea3
Reviewed-on: https://go-review.googlesource.com/13363
Reviewed-by: Austin Clements <austin@google.com>
2015-08-07 17:39:07 +00:00
Andrew Gerrand
0cd2999c3b cmd/go: replace code.google.com examples in docs with relevant repos
Change-Id: I625c9df161da2febdca85741c75fc32d4bef420b
Reviewed-on: https://go-review.googlesource.com/13344
Reviewed-by: Rob Pike <r@golang.org>
2015-08-07 05:52:11 +00:00
Andrew Gerrand
abe70aff0e doc: tweak phrasing in Go 1.5 release notes
Change-Id: I6bea045bb1cef15e6d9d3b4e6e6b4ae91f7bb941
Reviewed-on: https://go-review.googlesource.com/13345
Reviewed-by: Rob Pike <r@golang.org>
2015-08-07 05:51:33 +00:00
Russ Cox
4b145d42e9 doc: do not call WaitGroup a function
Fixes #12060.

Change-Id: Ie2fd10bedded1a4f4e0daa0c0c77ecd898480767
Reviewed-on: https://go-review.googlesource.com/13324
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
2015-08-06 20:37:38 +00:00
Austin Clements
ad731887a7 runtime: call goexit1 instead of goexit
Currently, runtime.Goexit() calls goexit()—the goroutine exit stub—to
terminate the goroutine. This *mostly* works, but can cause a
"leftover stack barriers" panic if the following happens:

1. Goroutine A has a reasonably large stack.

2. The garbage collector scan phase runs and installs stack barriers
   in A's stack. The top-most stack barrier happens to fall at address X.

3. Goroutine A unwinds the stack far enough to be a candidate for
   stack shrinking, but not past X.

4. Goroutine A calls runtime.Goexit(), which calls goexit(), which
   calls goexit1().

5. The garbage collector enters mark termination.

6. Goroutine A is preempted right at the prologue of goexit1() and
   performs a stack shrink, which calls gentraceback.

gentraceback stops as soon as it sees goexit on the stack, which is
only two frames up at this point, even though there may really be many
frames above it. More to the point, the stack barrier at X is above
the goexit frame, so gentraceback never sees that stack barrier. At
the end of gentraceback, it checks that it saw all of the stack
barriers and panics because it didn't see the one at X.

The fix is simple: call goexit1, which actually implements the process
of exiting a goroutine, rather than goexit, the exit stub.

To make sure this doesn't happen again in the future, we also add an
argument to the stub prototype of goexit so you really, really have to
want to call it in order to call it. We were able to reliably
reproduce the above sequence with a fair amount of awful code inserted
at the right places in the runtime, but chose to change the goexit
prototype to ensure this wouldn't happen again rather than pollute the
runtime with ugly testing code.

Change-Id: Ifb6fb53087e09a252baddadc36eebf954468f2a8
Reviewed-on: https://go-review.googlesource.com/13323
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-06 20:21:05 +00:00
Russ Cox
26baed6af7 runtime: fix race that dropped GoSysExit events from trace
This makes TestTraceStressStartStop much less flaky.
Running under stress, it changes the failure rate from
above 1/100 to under 1/50000. That very unlikely
failure happens when an unexpected GoSysExit is
written. Not sure how that happens yet, but it is much
less important.

Fixes #11953.

Change-Id: I034671936334b4f3ab733614ef239aa121d20247
Reviewed-on: https://go-review.googlesource.com/13321
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
2015-08-06 19:29:09 +00:00
Joe Shaw
5973558826 doc: remove duplicate -asmflags mention
Fixes #12053

Change-Id: Icd883b4f1ac944a8ec718c79770a8e3fc6542e3a
Reviewed-on: https://go-review.googlesource.com/13259
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-06 18:44:35 +00:00
Russ Cox
fced03a5c6 net/url: allow all valid host chars in RawPath
The old code was only allowing the chars we choose not to escape.
We sometimes prefer to escape chars that do not strictly need it.
Allowing those to be used in RawPath lets people override that
preference, which is in fact the whole point of RawPath (new in Go 1.5).

While we are here, also allow [ ] in RawPath.
This is not strictly spec-compliant, but it is what modern browers
do and what at least some people expect, and the [ ] do not cause
any ambiguity (the usual reason they would be escaped, as they are
part of the RFC gen-delims class).
The argument for allowing them now instead of waiting until Go 1.6
is that this way RawPath has one fixed meaning at the time it is
introduced, that we should not need to change or expand.

Fixes #5684.

Change-Id: If9c82a18f522d7ee1d10310a22821ada9286ee5c
Reviewed-on: https://go-review.googlesource.com/13258
Reviewed-by: Andrew Gerrand <adg@golang.org>
2015-08-06 02:59:16 +00:00
Russ Cox
e8be9a170c net/url: do not percent-encode valid host characters
The code in question was added as part of allowing zone identifiers
in IPv6 literals like http://[ipv6%zone]:port/foo, in golang.org/cl/2431.

The old condition makes no sense. It refers to §3.2.1, which is the wrong section
of the RFC, it excludes all the sub-delims, which §3.2.2 (the right section)
makes clear are valid, and it allows ':', which is not actually valid,
without an explanation as to why (because we keep :port in the Host field
of the URL struct).

The new condition allows all the sub-delims, as specified in RFC 3986,
plus the additional characters [ ] : seen in IP address literals and :port suffixes,
which we also keep in the Host field.

This allows mysql://a,b,c/path to continue to parse, as it did in Go 1.4 and earlier.

This CL does not break any existing tests, suggesting the over-conservative
behavior was not intended and perhaps not realized.

It is especially important not to over-escape the host field, because
Go does not unescape the host field during parsing: it rejects any
host field containing % characters.

Fixes #12036.

Change-Id: Iccbe4985957b3dc58b6dfb5dcb5b63a51a6feefb
Reviewed-on: https://go-review.googlesource.com/13254
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
2015-08-06 02:55:37 +00:00
Mikio Hara
91e3b35168 doc/go1.5.html: fix typo
Change-Id: Ic61fd38e7d2e0821c6adcaa210199a7dae8849a7
Reviewed-on: https://go-review.googlesource.com/13281
Reviewed-by: Andrew Gerrand <adg@golang.org>
2015-08-06 02:55:27 +00:00
Russ Cox
fc22331ccd net/url: restrict :port checking to [ipv6]:port form
Go 1.4 and earlier accepted mysql://x@y(z:123)/foo
and I don't see any compelling reason to break that.

The CL during Go 1.5 that broke this syntax was
trying to fix #11208 and was probably too aggressive.
I added a test case for #11208 to make sure that stays
fixed.

Relaxing the check did not re-break #11208 nor did
it cause any existing test to fail. I added a test for the
mysql://x@y(z:123)/foo syntax being preserved.

Fixes #12023.

Change-Id: I659d39f18c85111697732ad24b757169d69284fc
Reviewed-on: https://go-review.googlesource.com/13253
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
2015-08-06 02:55:03 +00:00
Andrew Gerrand
e38c801ad1 A+C: add Andy Maloney
Fixes #10639

Change-Id: I0aa3bcbf656e23e6a110041439f6052057074b88
Reviewed-on: https://go-review.googlesource.com/13270
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-05 23:16:22 +00:00
Russ Cox
0fb87abddf cmd/go: fix handling of vendored imports in foo_test.go files
Fixes #11977.
Fixes #11988.

Change-Id: I9f80006946d3752ee6d644ee51f2decfeaca1ff6
Reviewed-on: https://go-review.googlesource.com/13230
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
2015-08-05 23:13:19 +00:00
Robert Griesemer
98aa82287f spec: clarify semantics of built-in functions 'complex', 'real', and 'imag'
For #11669, #11540, #11945, #11946, #11947.

Change-Id: Ifb0053c498cee9f3473c396f9338d82bd856c110
Reviewed-on: https://go-review.googlesource.com/12860
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
2015-08-05 21:09:49 +00:00
Russ Cox
46a2913882 crypto/tls: fix ConnectionState().VerifiedChains for resumed connection
Strengthening VerifyHostname exposed the fact that for resumed
connections, ConnectionState().VerifiedChains was not being saved
and restored during the ClientSessionCache operations.
Do that.

This change just saves the verified chains in the client's session
cache. It does not re-verify the certificates when resuming a
connection.

There are arguments both ways about this: we want fast, light-weight
resumption connections (thus suggesting that we shouldn't verify) but
it could also be a little surprising that, if the verification config
is changed, that would be ignored if the same session cache is used.

On the server side we do re-verify client-auth certificates, but the
situation is a little different there. The client session cache is an
object in memory that's reset each time the process restarts. But the
server's session cache is a conceptual object, held by the clients, so
can persist across server restarts. Thus the chance of a change in
verification config being surprisingly ignored is much higher in the
server case.

Fixes #12024.

Change-Id: I3081029623322ce3d9f4f3819659fdd9a381db16
Reviewed-on: https://go-review.googlesource.com/13164
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
2015-08-05 19:59:28 +00:00
Russ Cox
0290d51b4a build: clean current tree in clean.bash
Otherwise clean.bash cleans $GOROOT, which might be something else entirely.

Fixes #12003.

Change-Id: I2ad5369017dde6db25f0c0514bc27c33d0a8bf54
Reviewed-on: https://go-review.googlesource.com/13251
Reviewed-by: David Crawshaw <crawshaw@golang.org>
2015-08-05 19:36:15 +00:00
Jed Denlea
26049f6f91 net/http: close server conn after broken trailers
Prior to this change, broken trailers would be handled by body.Read, and
an error would be returned to its caller (likely a Handler), but that
error would go completely unnoticed by the rest of the server flow
allowing a broken connection to be reused.  This is a possible request
smuggling vector.

Fixes #12027.

Change-Id: I077eb0b8dff35c5d5534ee5f6386127c9954bd58
Reviewed-on: https://go-review.googlesource.com/13148
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-05 19:30:24 +00:00
Adam Langley
f51b7fbdc4 crypto/tls: update testing certificates.
This change alters the certificate used in many tests so that it's no
longer self-signed. This allows some tests to exercise the standard
certificate verification paths in the future.

Change-Id: I9c3fcd6847eed8269ff3b86d9b6966406bf0642d
Reviewed-on: https://go-review.googlesource.com/13244
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
2015-08-05 19:06:51 +00:00
Russ Cox
b7fa8b557d go/build: fix internal/testenv dependency
Change-Id: Id1e30d70d6891ef12110f8e7832b94eeac9e2fa9
Reviewed-on: https://go-review.googlesource.com/13250
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-05 17:32:43 +00:00
Austin Clements
d57f037302 runtime: don't recheck heap trigger for periodic GC
88e945f introduced a non-speculative double check of the heap trigger
before actually starting a concurrent GC. This was necessary to fix a
race for heap-triggered GC, but broke sysmon-triggered periodic GC,
since the heap check will of course fail for periodically triggered
GC.

Fix this by telling startGC whether or not this GC was triggered by
heap size or a timer and only doing the heap size double check for GCs
triggered by heap size.

Fixes #12026.

Change-Id: I7c3f6ec364545c36d619f2b4b3bf3b758e3bcbd6
Reviewed-on: https://go-review.googlesource.com/13168
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-05 17:28:56 +00:00
Robert Griesemer
3dd3ab41ac spec: better organization of arithmetic operator section
First step towards cleaning up the operator section - no language
changes. Specifically:

- Grouped arithmetic operations by types (integer, floating-point,
  string), with corresponding h4 headings.

- Changed Operator precedence title from h3 to h4.

- Moved Integer Overflow section after integer operations and changed
  its title from h3 to h4.

This puts things that belong together closer. No heading id's were
lost (in case of references from outside the spec).

Change-Id: I6b349ba8d86a6ae29b596beb297cc45c81e69399
Reviewed-on: https://go-review.googlesource.com/13143
Reviewed-by: Rob Pike <r@golang.org>
2015-08-05 17:05:07 +00:00
Robert Griesemer
05614bfcfa spec: fix inconsistency of visibility rules for method names
Inconsistency identified by Anmol Sethi (anmol@aubble.com).

Fixes #10341.

Change-Id: I1a1f5b22aad29b56280f81026feaa37a61b3e0a9
Reviewed-on: https://go-review.googlesource.com/13132
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-05 17:03:36 +00:00
Robert Griesemer
85789daac3 spec: clarify that short variable declarations can redeclare parameters
Fixes #9837.

Change-Id: Ia513c7e5db221eee8e3ab0affa6d3688d2099fd9
Reviewed-on: https://go-review.googlesource.com/13130
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-05 17:01:05 +00:00
Robert Griesemer
87c8707e6f spec: clarify sentence about non-constant shifts
Fixes #10514.

Change-Id: Iae95a304d3ebb1ed82567aa234e05dc434db984f
Reviewed-on: https://go-review.googlesource.com/13098
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-05 17:00:11 +00:00
Russ Cox
1579822be1 doc/go1.5: fix hyperlink for runtime/trace
Missed in CL 13074.

Change-Id: Ic0600341abbc423cd8d7b2201bf50e3b0bf398a7
Reviewed-on: https://go-review.googlesource.com/13167
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2015-08-05 16:14:45 +00:00
Russ Cox
47e0e4233f go/build: enable cgo on freebsd/arm
Now that it works we need to turn it back on.

Fixes #10119.

Change-Id: I9c62d3026f7bb62c49a601ad73f33bf655372915
Reviewed-on: https://go-review.googlesource.com/13162
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2015-08-05 16:14:05 +00:00
Russ Cox
7d9faaa19f cmd/go: skip external tests on freebsd-arm builder
It is just far too slow.
I have a CL for Go 1.6 that makes many of these into internal tests.
That will improve the coverage.

It does not matter much, because basically none of the go command
tests are architecture dependent, so the other builders will catch
any problems.

Fixes freebsd-arm builder.

Change-Id: I8b2f6ac2cc1e7657019f7731c6662dc43e20bfb5
Reviewed-on: https://go-review.googlesource.com/13166
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2015-08-05 16:13:37 +00:00
Russ Cox
7721ac0535 internal/testenv: add Builder, to report builder name
This works after golang.org/cl/13120 is running on the
coordinator (maybe it already is).

Change-Id: I4053d8e2f32fafd47b927203a6f66d5858e23376
Reviewed-on: https://go-review.googlesource.com/13165
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2015-08-05 16:13:25 +00:00
Austin Clements
43a404cf5f doc: mention new DWARF line table decoder in go1.5.html
Change-Id: I4e8c20284255e0e17b6fb72475d2d37f49994788
Reviewed-on: https://go-review.googlesource.com/13113
Reviewed-by: Rob Pike <r@golang.org>
2015-08-05 14:59:24 +00:00
Dmitry Vyukov
de641ef0c4 doc/go1.5.html: update references to runtime/trace package
Tracing functionality was moved from runtime/pprof to runtime/trace.

Change-Id: I694e0f209d043c7ffecb113f1825175bf963dde3
Reviewed-on: https://go-review.googlesource.com/13074
Reviewed-by: Rob Pike <r@golang.org>
2015-08-05 08:13:15 +00:00
Russ Cox
2a60d77059 runtime: align stack pointer during initcgo call on arm
This is what is causing freebsd/arm to crash mysteriously when using cgo.
The bug was introduced in golang.org/cl/4030, which moved this code out
of rt0_go and into its own function. The ARM ABI says that calls must
be made with the stack pointer at an 8-byte boundary, but only FreeBSD
seems to crash when this is violated.

Fixes #10119.

Change-Id: Ibdbe76b2c7b80943ab66b8abbb38b47acb70b1e5
Reviewed-on: https://go-review.googlesource.com/13161
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
2015-08-05 05:31:34 +00:00
Andrew Gerrand
31b0b73924 doc: adjust installation instructions dynamically for a given download
This change allows the download page to redirect the user to
/doc/install?download=filename so the user can see installation
instructions specific to the file they are downloading.

This change also expands the "Test your Go installation" section
to instruct the user to create a workspace, hopefully leading
to less confusion down the line.

It also changes the front page download link to go directly
to the downloads page, which will in turn take them to the
installation instructions (the original destination).

This is related to this change to the tools repo:
https://golang.org/cl/13180

Change-Id: I658327bdb93ad228fb1846e389b281b15da91b1d
Reviewed-on: https://go-review.googlesource.com/13151
Reviewed-by: Chris Broadfoot <cbro@golang.org>
2015-08-05 04:18:56 +00:00
Andrew Gerrand
e019767ecb doc: bump minimum requirement to OS X 10.7
Fixes #11995

Change-Id: I9e2901d77ebde705f59822e7d4a8163cbacffcd7
Reviewed-on: https://go-review.googlesource.com/13150
Reviewed-by: Rob Pike <r@golang.org>
2015-08-05 00:52:00 +00:00
Robert Griesemer
3cfc34a555 reflect: fix doc string
Fixes #12017.

Change-Id: I3dfcf9d0b62cae02eca1973383f0aad286a6ef4d
Reviewed-on: https://go-review.googlesource.com/13136
Reviewed-by: Keith Randall <khr@golang.org>
2015-08-04 21:10:58 +00:00
Austin Clements
be39a42920 runtime: fix typos in comments
Change-Id: I66f7937b22bb6e05c3f2f0f2a057151020ad9699
Reviewed-on: https://go-review.googlesource.com/13049
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-04 18:54:56 +00:00
Austin Clements
e3870aa6f3 runtime: fix assist utilization computation
When commit 510fd13 enabled assists during the scan phase, it failed
to also update the code in the GC controller that computed the assist
CPU utilization and adjusted the trigger based on it. Fix that code so
it uses the start of the scan phase as the wall-clock time when
assists were enabled rather than the start of the mark phase.

Change-Id: I05013734b4448c3e2c730dc7b0b5ee28c86ed8cf
Reviewed-on: https://go-review.googlesource.com/13048
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-04 18:54:53 +00:00
Austin Clements
1fb01a88f9 runtime: revise assist ratio aggressively
At the start of a GC cycle, the garbage collector computes the assist
ratio based on the total scannable heap size. This was intended to be
conservative; after all, this assumes the entire heap may be reachable
and hence needs to be scanned. But it only assumes that the *current*
entire heap may be reachable. It fails to account for heap allocated
during the GC cycle. If the trigger ratio is very low (near zero), and
most of the heap is reachable when GC starts (which is likely if the
trigger ratio is near zero), then it's possible for the mutator to
create new, reachable heap fast enough that the assists won't keep up
based on the assist ratio computed at the beginning of the cycle. As a
result, the heap can grow beyond the heap goal (by hundreds of megs in
stress tests like in issue #11911).

We already have some vestigial logic for dealing with situations like
this; it just doesn't run often enough. Currently, every 10 ms during
the GC cycle, the GC revises the assist ratio. This was put in before
we switched to a conservative assist ratio (when we really were using
estimates of scannable heap), and it turns out to be exactly what we
need now. However, every 10 ms is far too infrequent for a rapidly
allocating mutator.

This commit reuses this logic, but replaces the 10 ms timer with
revising the assist ratio every time the heap is locked, which
coincides precisely with when the statistics used to compute the
assist ratio are updated.

Fixes #11911.

Change-Id: I377b231ab064946228378fa10422a46d1b50f4c5
Reviewed-on: https://go-review.googlesource.com/13047
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-04 18:54:48 +00:00
Austin Clements
f9dc3382ad runtime: when gcpacertrace > 0, print information about assist ratio
This was useful in debugging the mutator assist behavior for #11911,
and it fits with the other gcpacertrace output.

Change-Id: I1e25590bb4098223a160de796578bd11086309c7
Reviewed-on: https://go-review.googlesource.com/13046
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-04 18:54:46 +00:00
Austin Clements
fc9ca85f4c runtime: make sweep proportional to spans bytes allocated
Proportional concurrent sweep is currently based on a ratio of spans
to be swept per bytes of object allocation. However, proportional
sweeping is performed during span allocation, not object allocation,
in order to minimize contention and overhead. Since objects are
allocated from spans after those spans are allocated, the system tends
to operate in debt, which means when the next GC cycle starts, there
is often sweep debt remaining, so GC has to finish the sweep, which
delays the start of the cycle and delays enabling mutator assists.

For example, it's quite likely that many Ps will simultaneously refill
their span caches immediately after a GC cycle (because GC flushes the
span caches), but at this point, there has been very little object
allocation since the end of GC, so very little sweeping is done. The
Ps then allocate objects from these cached spans, which drives up the
bytes of object allocation, but since these allocations are coming
from cached spans, nothing considers whether more sweeping has to
happen. If the sweep ratio is high enough (which can happen if the
next GC trigger is very close to the retained heap size), this can
easily represent a sweep debt of thousands of pages.

Fix this by making proportional sweep proportional to the number of
bytes of spans allocated, rather than the number of bytes of objects
allocated. Prior to allocating a span, both the small object path and
the large object path ensure credit for allocating that span, so the
system operates in the black, rather than in the red.

Combined with the previous commit, this should eliminate all sweeping
from GC start up. On the stress test in issue #11911, this reduces the
time spent sweeping during GC (and delaying start up) by several
orders of magnitude:

                mean    99%ile     max
    pre fix      1 ms    11 ms   144 ms
    post fix   270 ns   735 ns   916 ns

Updates #11911.

Change-Id: I89223712883954c9d6ec2a7a51ecb97172097df3
Reviewed-on: https://go-review.googlesource.com/13044
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-04 18:54:44 +00:00
Austin Clements
e30c6d64ba runtime: always give concurrent sweep some heap distance
Currently it's possible for the next_gc heap size trigger computed for
the next GC cycle to be less than the current allocated heap size.
This means the next cycle will start immediately, which means there's
no time to perform the concurrent sweep between GC cycles. This places
responsibility for finishing the sweep on GC itself, which delays GC
start-up and hence delays mutator assist.

Fix this by ensuring that next_gc is always at least a little higher
than the allocated heap size, so we won't trigger the next cycle
instantly.

Updates #11911.

Change-Id: I74f0b887bf187518d5fedffc7989817cbcf30592
Reviewed-on: https://go-review.googlesource.com/13043
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
2015-08-04 18:54:41 +00:00
Austin Clements
fb5230af8a runtime: assist the GC during GC startup and shutdown
Currently there are two sensitive periods during which a mutator can
allocate past the heap goal but mutator assists can't be enabled: 1)
at the beginning of GC between when the heap first passes the heap
trigger and sweep termination and 2) at the end of GC between mark
termination and when the background GC goroutine parks. During these
periods there's no back-pressure or safety net, so a rapidly
allocating mutator can allocate past the heap goal. This is
exacerbated if there are many goroutines because the GC coordinator is
scheduled as any other goroutine, so if it gets preempted during one
of these periods, it may stay preempted for a long period (10s or 100s
of milliseconds).

Normally the mutator does scan work to create back-pressure against
allocation, but there is no scan work during these periods. Hence, as
a fall back, if a mutator would assist but can't yet, simply yield the
CPU. This delays the mutator somewhat, but more importantly gives more
CPU time to the GC coordinator for it to complete the transition.

This is obviously a workaround. Issue #11970 suggests a far better but
far more invasive way to fix this.

Updates #11911. (This very nearly fixes the issue, but about once
every 15 minutes I get a GC cycle where the assists are enabled but
don't do enough work.)

Change-Id: I9768b79e3778abd3e06d306596c3bd77f65bf3f1
Reviewed-on: https://go-review.googlesource.com/13026
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
2015-08-04 18:54:38 +00:00