The motivation is that sysAlloc/Free() currently aren't safe to be
called without a valid G, because arm's xadd64() uses locks that require
a valid G.

The solution here was proposed by Dmitry Vyukov: use xadduintptr()
instead of xadd64(), until arm can support xadd64 on all of its
architectures (not a trivial task for arm).

Change-Id: I250252079357ea2e4360e1235958b1c22051498f
Reviewed-on: https://go-review.googlesource.com/9002Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

- main3.c tests main.main is exported when compiled for GOOS=android.
- wait longer for main2.c (it's slow on android/arm)
- rearranged test.bash

Fixes #10070.

Change-Id: I6e5a98d1c5fae776afa54ecb5da633b59b269316
Reviewed-on: https://go-review.googlesource.com/9296Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>

This lets us avoid loading string constants via the GOT and (together with
http://golang.org/cl/9102) results in the fannkuch benchmark having very similar
register usage with -dynlink as without.

Change-Id: Ic3892b399074982b76773c3e547cfbba5dabb6f9
Reviewed-on: https://go-review.googlesource.com/9103Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

Currently, when allocation reaches the GC trigger, the runtime uses
readyExecute to start the GC goroutine immediately rather than wait
for the scheduler to get around to the GC goroutine while the mutator
continues to grow the heap.

Now that the scheduler runs the most recently readied goroutine when a
goroutine yields its time slice, this rigmarole is no longer
necessary. The runtime can simply ready the GC goroutine and yield
from the readying goroutine.

Change-Id: I3b4ebadd2a72a923b1389f7598f82973dd5c8710
Reviewed-on: https://go-review.googlesource.com/9292Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Austin Clements <austin@google.com>

Currently, the main GC goroutine sleeps on a note during concurrent
mark and the first background mark worker or assist to finish marking
use wakes up that note to let the main goroutine proceed into mark
termination. Unfortunately, the latency of this wakeup can be quite
high, since the GC goroutine will typically have lost its P while in
the futex sleep, meaning it will be placed on the global run queue and
will wait there until some P is kind enough to pick it up. This delay
gives the mutator more time to allocate and create floating garbage,
growing the heap unnecessarily. Worse, it's likely that background
marking has stopped at this point (unless GOMAXPROCS>4), so anything
that's allocated and published to the heap during this window will
have to be scanned during mark termination while the world is stopped.

This change replaces the note sleep/wakeup with a gopark/ready
scheme. This keeps the wakeup inside the Go scheduler and lets the
garbage collector take advantage of the new scheduler semantics that
run the ready()d goroutine immediately when the ready()ing goroutine
sleeps.

For the json benchmark from x/benchmarks with GOMAXPROCS=4, this
reduces the delay in waking up the GC goroutine and entering mark
termination once concurrent marking is done from ~100ms to typically
<100µs.

Change-Id: Ib11f8b581b8914f2d68e0094f121e49bac3bb384
Reviewed-on: https://go-review.googlesource.com/9291Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Currently, we use a note sleep with a timeout in a loop in func gc to
periodically revise the GC control variables. Replace this with a
fully blocking note sleep and use a periodic timer to trigger the
revise instead. This is a step toward replacing the note sleep in func
gc.

Change-Id: I2d562f6b9b2e5f0c28e9a54227e2c0f8a2603f63
Reviewed-on: https://go-review.googlesource.com/9290Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Currently, when the runtime ready()s a G, it adds it to the end of the
current P's run queue and continues running. If there are many other
things in the run queue, this can result in a significant delay before
the ready()d G actually runs and can hurt fairness when other Gs in
the run queue are CPU hogs. For example, if there are three Gs sharing
a P, one of which is a CPU hog that never voluntarily gives up the P
and the other two of which are doing small amounts of work and
communicating back and forth on an unbuffered channel, the two
communicating Gs will get very little CPU time.

Change this so that when G1 ready()s G2 and then blocks, the scheduler
immediately hands off the remainder of G1's time slice to G2. In the
above example, the two communicating Gs will now act as a unit and
together get half of the CPU time, while the CPU hog gets the other
half of the CPU time.

This fixes the problem demonstrated by the ping-pong benchmark added
in the previous commit:

benchmark                old ns/op     new ns/op     delta
BenchmarkPingPongHog     684287        825           -99.88%

On the x/benchmarks suite, this change improves the performance of
garbage by ~6% (for GOMAXPROCS=1 and 4), and json by 28% and 36% for
GOMAXPROCS=1 and 4. It has negligible effect on heap size.

This has no effect on the go1 benchmark suite since those benchmarks
are mostly single-threaded.

Change-Id: I858a08eaa78f702ea98a5fac99d28a4ac91d339f
Reviewed-on: https://go-review.googlesource.com/9289Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

This benchmark demonstrates a current problem with the scheduler where
a set of frequently communicating goroutines get very little CPU time
in the presence of another goroutine that hogs that CPU, even if one
of those communicating goroutines is always runnable.

Currently it takes about 0.5 milliseconds to switch between
ping-ponging goroutines in the presence of a CPU hog:

BenchmarkPingPongHog	    2000	    684287 ns/op

Change-Id: I278848c84f778de32344921ae8a4a8056e4898b0
Reviewed-on: https://go-review.googlesource.com/9288Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

There are a variety of places where we check if a P's run queue is
empty. This test is about to get slightly more complicated, so factor
it out into a new function, runqempty. This function is inlinable, so
this has no effect on performance.

Change-Id: If4a0b01ffbd004937de90d8d686f6ded4aad2c6b
Reviewed-on: https://go-review.googlesource.com/9287Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

We can expand the test cases as we discover problems.
This is some basic tests plus all the things I got wrong
in some recent work.

Change-Id: Id875fcfaf74eb087ae42b441fe47a34c5b8ccb39
Reviewed-on: https://go-review.googlesource.com/9158Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

Explicitly specify that we represent polynomial in reversed notation

Fixes #8229

Change-Id: Idf094c01fd82f133cd0c1b50fa967d12c577bdb5
Reviewed-on: https://go-review.googlesource.com/9237Reviewed-by: David Chase <drchase@google.com>

Some machines are so slow that even with the default timeoutScale,
they still timeout some tests. For example, currently some linux/arm
builders and the openbsd/arm builder are timing out the runtime
test and CL 8397 was proposed to skip some tests on openbsd/arm
to fix the build.

Instead of increasing timeoutScale or skipping tests, this CL
introduces an environment variable $GO_TEST_TIMEOUT_SCALE that
could be set to manually set a larger timeoutScale for those
machines/builders.

Fixes #10314.

Change-Id: I16c9a9eb980d6a63309e4cacd79eee2fe05769ee
Reviewed-on: https://go-review.googlesource.com/9223Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Forward signals to signal handlers installed before Go installs its own,
under certain circumstances.  In particular, as iant@ suggests, signals are
forwarded iff:
   (1) a non-SIG_DFL signal handler existed before Go, and
   (2) signal is synchronous (i.e., one of SIGSEGV, SIGBUS, SIGFPE), and
   	(3a) signal occured on a non-Go thread, or
   	(3b) signal occurred on a Go thread but in CGo code.

Supported only on Linux, for now.

Change-Id: I403219ee47b26cf65da819fb86cf1ec04d3e25f5
Reviewed-on: https://go-review.googlesource.com/8712Reviewed-by: Ian Lance Taylor <iant@golang.org>

benchmark                   old ns/op     new ns/op     delta
BenchmarkEncodeToString     31281         23821         -23.85%
BenchmarkDecodeString       156508        82254         -47.44%

benchmark                   old MB/s     new MB/s     speedup
BenchmarkEncodeToString     261.88       343.89       1.31x
BenchmarkDecodeString       69.80        132.81       1.90x

Change-Id: I115e0b18c3a6d5ef6bfdcb3f637644f02f290907
Reviewed-on: https://go-review.googlesource.com/8808Reviewed-by: Nigel Tao <nigeltao@golang.org>

They are vestiges of the c2go transition.

Change-Id: I22672e40373ef77d7a0bf69cfff8017e46353055
Reviewed-on: https://go-review.googlesource.com/9265Reviewed-by: Minux Ma <minux@golang.org>

benchmark                       old ns/op      new ns/op      delta
BenchmarkAddVV_1                18.7           14.8           -20.86%
BenchmarkAddVV_2                21.8           16.6           -23.85%
BenchmarkAddVV_3                26.1           17.1           -34.48%
BenchmarkAddVV_4                30.4           21.9           -27.96%
BenchmarkAddVV_5                35.5           19.8           -44.23%
BenchmarkAddVV_1e1              63.0           28.3           -55.08%
BenchmarkAddVV_1e2              593            178            -69.98%
BenchmarkAddVV_1e3              5691           1490           -73.82%
BenchmarkAddVV_1e4              56868          20761          -63.49%
BenchmarkAddVV_1e5              569062         207679         -63.51%
BenchmarkAddVW_1                15.8           12.6           -20.25%
BenchmarkAddVW_2                17.8           13.1           -26.40%
BenchmarkAddVW_3                21.2           13.9           -34.43%
BenchmarkAddVW_4                23.6           14.7           -37.71%
BenchmarkAddVW_5                26.0           15.8           -39.23%
BenchmarkAddVW_1e1              41.3           21.6           -47.70%
BenchmarkAddVW_1e2              383            145            -62.14%
BenchmarkAddVW_1e3              3703           1264           -65.87%
BenchmarkAddVW_1e4              36920          14359          -61.11%
BenchmarkAddVW_1e5              370345         143046         -61.37%
BenchmarkAddMulVVW_1            33.2           32.5           -2.11%
BenchmarkAddMulVVW_2            58.0           57.2           -1.38%
BenchmarkAddMulVVW_3            95.2           93.9           -1.37%
BenchmarkAddMulVVW_4            108            106            -1.85%
BenchmarkAddMulVVW_5            159            156            -1.89%
BenchmarkAddMulVVW_1e1          344            340            -1.16%
BenchmarkAddMulVVW_1e2          3644           3624           -0.55%
BenchmarkAddMulVVW_1e3          37344          37208          -0.36%
BenchmarkAddMulVVW_1e4          373295         372170         -0.30%
BenchmarkAddMulVVW_1e5          3438116        3425606        -0.36%
BenchmarkBitLen0                7.21           4.32           -40.08%
BenchmarkBitLen1                6.49           4.32           -33.44%
BenchmarkBitLen2                7.23           4.32           -40.25%
BenchmarkBitLen3                6.49           4.32           -33.44%
BenchmarkBitLen4                7.22           4.32           -40.17%
BenchmarkBitLen5                6.52           4.33           -33.59%
BenchmarkBitLen8                7.22           4.32           -40.17%
BenchmarkBitLen9                6.49           4.32           -33.44%
BenchmarkBitLen16               8.66           4.32           -50.12%
BenchmarkBitLen17               7.95           4.32           -45.66%
BenchmarkBitLen31               8.69           4.32           -50.29%
BenchmarkGCD10x10               5021           5033           +0.24%
BenchmarkGCD10x100              5571           5572           +0.02%
BenchmarkGCD10x1000             6707           6729           +0.33%
BenchmarkGCD10x10000            13526          13419          -0.79%
BenchmarkGCD10x100000           85668          83242          -2.83%
BenchmarkGCD100x100             24196          23936          -1.07%
BenchmarkGCD100x1000            28802          27309          -5.18%
BenchmarkGCD100x10000           64111          51704          -19.35%
BenchmarkGCD100x100000          385840         274385         -28.89%
BenchmarkGCD1000x1000           262892         236269         -10.13%
BenchmarkGCD1000x10000          371393         277883         -25.18%
BenchmarkGCD1000x100000         1311795        589055         -55.10%
BenchmarkGCD10000x10000         9596740        6123930        -36.19%
BenchmarkGCD10000x100000        16404000       7269610        -55.68%
BenchmarkGCD100000x100000       776660000      419270000      -46.02%
BenchmarkHilbert                13478980       13402270       -0.57%
BenchmarkBinomial               9802           9440           -3.69%
BenchmarkBitset                 142            142            +0.00%
BenchmarkBitsetNeg              328            279            -14.94%
BenchmarkBitsetOrig             853            861            +0.94%
BenchmarkBitsetNegOrig          1489           1444           -3.02%
BenchmarkMul                    420949000      410481000      -2.49%
BenchmarkExp3Power0x10          1148           1229           +7.06%
BenchmarkExp3Power0x40          1322           1376           +4.08%
BenchmarkExp3Power0x100         2437           2486           +2.01%
BenchmarkExp3Power0x400         9456           9346           -1.16%
BenchmarkExp3Power0x1000        113623         108701         -4.33%
BenchmarkExp3Power0x4000        1134933        1101481        -2.95%
BenchmarkExp3Power0x10000       10773570       10396160       -3.50%
BenchmarkExp3Power0x40000       101362100      97788300       -3.53%
BenchmarkExp3Power0x100000      921114000      885249000      -3.89%
BenchmarkExp3Power0x400000      8323094000     7969020000     -4.25%
BenchmarkFibo                   322021600      92554450       -71.26%
BenchmarkScanPi                 1264583        321065         -74.61%
BenchmarkStringPiParallel       1644661        554216         -66.30%
BenchmarkScan10Base2            1111           1080           -2.79%
BenchmarkScan100Base2           6645           6345           -4.51%
BenchmarkScan1000Base2          84084          62405          -25.78%
BenchmarkScan10000Base2         3105998        932551         -69.98%
BenchmarkScan100000Base2        257234800      40113333       -84.41%
BenchmarkScan10Base8            571            573            +0.35%
BenchmarkScan100Base8           2810           2543           -9.50%
BenchmarkScan1000Base8          47383          25834          -45.48%
BenchmarkScan10000Base8         2739518        567203         -79.30%
BenchmarkScan100000Base8        253952400      36495680       -85.63%
BenchmarkScan10Base10           553            556            +0.54%
BenchmarkScan100Base10          2640           2385           -9.66%
BenchmarkScan1000Base10         50865          24049          -52.72%
BenchmarkScan10000Base10        3279916        549313         -83.25%
BenchmarkScan100000Base10       309121000      36213140       -88.29%
BenchmarkScan10Base16           478            483            +1.05%
BenchmarkScan100Base16          2353           2144           -8.88%
BenchmarkScan1000Base16         48091          24246          -49.58%
BenchmarkScan10000Base16        2858886        586475         -79.49%
BenchmarkScan100000Base16       266320000      38190500       -85.66%
BenchmarkString10Base2          736            730            -0.82%
BenchmarkString100Base2         2695           2707           +0.45%
BenchmarkString1000Base2        20549          20388          -0.78%
BenchmarkString10000Base2       212638         210782         -0.87%
BenchmarkString100000Base2      1944963        1938033        -0.36%
BenchmarkString10Base8          524            517            -1.34%
BenchmarkString100Base8         1326           1320           -0.45%
BenchmarkString1000Base8        8213           8249           +0.44%
BenchmarkString10000Base8       72204          72092          -0.16%
BenchmarkString100000Base8      769068         765993         -0.40%
BenchmarkString10Base10         1018           982            -3.54%
BenchmarkString100Base10        3485           3206           -8.01%
BenchmarkString1000Base10       37102          18935          -48.97%
BenchmarkString10000Base10      188633         88637          -53.01%
BenchmarkString100000Base10     124490300      19700940       -84.17%
BenchmarkString10Base16         509            502            -1.38%
BenchmarkString100Base16        1084           1098           +1.29%
BenchmarkString1000Base16       5641           5650           +0.16%
BenchmarkString10000Base16      46900          46745          -0.33%
BenchmarkString100000Base16     508957         505840         -0.61%
BenchmarkLeafSize0              8934320        8149465        -8.78%
BenchmarkLeafSize1              237666         118381         -50.19%
BenchmarkLeafSize2              237807         117854         -50.44%
BenchmarkLeafSize3              1688640        353494         -79.07%
BenchmarkLeafSize4              235676         116196         -50.70%
BenchmarkLeafSize5              2121896        430325         -79.72%
BenchmarkLeafSize6              1682306        351775         -79.09%
BenchmarkLeafSize7              1051847        251436         -76.10%
BenchmarkLeafSize8              232697         115674         -50.29%
BenchmarkLeafSize9              2403616        488443         -79.68%
BenchmarkLeafSize10             2120975        429545         -79.75%
BenchmarkLeafSize11             2023789        426525         -78.92%
BenchmarkLeafSize12             1684830        351985         -79.11%
BenchmarkLeafSize13             1465529        337906         -76.94%
BenchmarkLeafSize14             1050498        253872         -75.83%
BenchmarkLeafSize15             683228         197384         -71.11%
BenchmarkLeafSize16             232496         116026         -50.10%
BenchmarkLeafSize32             245841         126671         -48.47%
BenchmarkLeafSize64             301728         190285         -36.93%

Change-Id: I63e63297896d96b89c9a275b893c2b405a7e105d
Reviewed-on: https://go-review.googlesource.com/9260Reviewed-by: David Crawshaw <crawshaw@golang.org>

This addresses iant's comments from CL 9164.

Change-Id: I7b5b282f61b11aab587402c2d302697e76666376
Reviewed-on: https://go-review.googlesource.com/9222Reviewed-by: Ian Lance Taylor <iant@golang.org>

Currently, it's possible for the next_gc calculation to underflow.
Since next_gc is unsigned, this wraps around and effectively disables
GC for the rest of the program's execution. Besides being obviously
wrong, this is causing test failures on 32-bit because some tests are
running out of heap.

This underflow happens for two reasons, both having to do with how we
estimate the reachable heap size at the end of the GC cycle.

One reason is that this calculation depends on the value of heap_live
at the beginning of the GC cycle, but we currently only record that
value during a concurrent GC and not during a forced STW GC. Fix this
by moving the recorded value from gcController to work and recording
it on a common code path.

The other reason is that we use the amount of allocation during the GC
cycle as an approximation of the amount of floating garbage and
subtract it from the marked heap to estimate the reachable heap.
However, since this is only an approximation, it's possible for the
amount of allocation during the cycle to be *larger* than the marked
heap size (since the runtime allocates white and it's possible for
these allocations to never be made reachable from the heap). Currently
this causes wrap-around in our estimate of the reachable heap size,
which in turn causes wrap-around in next_gc. Fix this by bottoming out
the reachable heap estimate at 0, in which case we just fall back to
triggering GC at heapminimum (which is okay since this only happens on
small heaps).

Fixes #10555, fixes #10556, and fixes #10559.

Change-Id: Iad07b529c03772356fede2ae557732f13ebfdb63
Reviewed-on: https://go-review.googlesource.com/9286
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Rick Hudson <rlh@golang.org>

To achieve a 2% improvement in the garbage benchmark this CL removes
an unneeded assert and avoids one hbits.next() call per object
being scanned.

Change-Id: Ibd542d01e9c23eace42228886f9edc488354df0d
Reviewed-on: https://go-review.googlesource.com/9244Reviewed-by: Austin Clements <austin@google.com>

newosproc0 does not work on android/arm.
See issue #10548.

Change-Id: Ieaf6f5d0b77cddf5bf0b6c89fd12b1c1b8723f9b
Reviewed-on: https://go-review.googlesource.com/9293Reviewed-by: David Crawshaw <crawshaw@golang.org>

lands exactly on an IDAT row boundary.

Fixes #10493

Change-Id: I12be7c5bdcde7032e17ed1d4400db5f17c72bc87
Reviewed-on: https://go-review.googlesource.com/9270Reviewed-by: Rob Pike <r@golang.org>

github.com/kr/goven says it's deprecated and anyway
it would be preferable to point users to a standard Go tool.

Change-Id: Iac4a0d13233604a36538748d498f5770b2afce19
Reviewed-on: https://go-review.googlesource.com/8969Reviewed-by: Minux Ma <minux@golang.org>

If the machine's network configuration files (resolv.conf,
nsswitch.conf) don't have any unsupported options, prefer Go's DNS
resolver, which doesn't have the cgo & thread over.

It means users can have more than 500 DNS requests outstanding (our
current limit for cgo lookups) and not have one blocked thread per
outstanding request.

Discussed in thread https://groups.google.com/d/msg/golang-dev/2ZUi792oztM/Q0rg_DkF5HMJ

Change-Id: I3f685d70aff6b47bec30b63e9fba674b20507f95
Reviewed-on: https://go-review.googlesource.com/8945Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

They are vestiges of the c2go translation.

Change-Id: I9a10536f5986b751a35cc7d84b5ba69ae0c2ede7
Reviewed-on: https://go-review.googlesource.com/9262Reviewed-by: Minux Ma <minux@golang.org>

MiB.

Fixes #10531

Change-Id: I9eece86837c3df2b1f7df315d5ec94bd3ede3eec
Reviewed-on: https://go-review.googlesource.com/9238
Run-TryBot: Nigel Tao <nigeltao@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

There is an assumption that the function executed in child thread
created by runtime.close should not return. And different systems
enforce that differently: some exit that thread, some exit the
whole process.

The test TestNewOSProc0 introduced in CL 9161 breaks that assumption,
so we need to adjust the code to only exit the thread should the
called function return.

Change-Id: Id631cb2f02ec6fbd765508377a79f3f96c6a2ed6
Reviewed-on: https://go-review.googlesource.com/9246Reviewed-by: Dave Cheney <dave@cheney.net>

It was only visible when you run godoc with explicit GOOS=windows,
which is less useful for people developing portable application on
non-windows platforms.

Also added a note that log/syslog is not supported on NaCl.

Change-Id: I81650445fb2a5ee161da7e0608c3d3547d5ac2a6
Reviewed-on: https://go-review.googlesource.com/9245Reviewed-by: Ian Lance Taylor <iant@golang.org>

The constants in cmd/internal/goobj had gone stale (we had three copies of
these constants, working on reducing that was what got me to noticing this).

Some of the changes to link.hello.darwin.amd64 are the change from absolute
to %rip-relative addressing, a change which happened quite a while ago...

Depends on http://golang.org/cl/9113.

Fixes #10501.

Change-Id: Iaa1511f458a32228c2df2ccd0076bb9ae212a035
Reviewed-on: https://go-review.googlesource.com/9105Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Currently, we set the heap goal for the next GC cycle using the size
of the marked heap at the end of the current cycle. This can lead to a
bad feedback loop if the mutator is rapidly allocating and releasing
pointers that can significantly bloat heap size.

If the GC were STW, the marked heap size would be exactly the
reachable heap size (call it stwLive). However, in concurrent GC,
marked=stwLive+floatLive, where floatLive is the amount of "floating
garbage": objects that were reachable at some point during the cycle
and were marked, but which are no longer reachable by the end of the
cycle. If the GC cycle is short, then the mutator doesn't have much
time to create floating garbage, so marked≈stwLive. However, if the GC
cycle is long and the mutator is allocating and creating floating
garbage very rapidly, then it's possible that marked≫stwLive. Since
the runtime currently sets the heap goal based on marked, this will
cause it to set a high heap goal. This means that 1) the next GC cycle
will take longer because of the larger heap and 2) the assist ratio
will be low because of the large distance between the trigger and the
goal. The combination of these lets the mutator produce even more
floating garbage in the next cycle, which further exacerbates the
problem.

For example, on the garbage benchmark with GOMAXPROCS=1, this causes
the heap to grow to ~500MB and the garbage collector to retain upwards
of ~300MB of heap, while the true reachable heap size is ~32MB. This,
in turn, causes the GC cycle to take upwards of ~3 seconds.

Fix this bad feedback loop by estimating the true reachable heap size
(stwLive) and using this rather than the marked heap size
(stwLive+floatLive) as the basis for the GC trigger and heap goal.
This breaks the bad feedback loop and causes the mutator to assist
more, which decreases the rate at which it can create floating
garbage. On the same garbage benchmark, this reduces the maximum heap
size to ~73MB, the retained heap to ~40MB, and the duration of the GC
cycle to ~200ms.

Change-Id: I7712244c94240743b266f9eb720c03802799cdd1
Reviewed-on: https://go-review.googlesource.com/9177Reviewed-by: Rick Hudson <rlh@golang.org>

Change-Id: I429402dd91243cd9415b054ee17bfebccc68ed57
Reviewed-on: https://go-review.googlesource.com/9197Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

This may or may not be useful to the end user, but it's incredibly
useful for us to understand the behavior of the pacer. Currently this
is fairly easy (though not trivial) to derive from the other heap
stats we print, but we're about to change how we compute the goal,
which will make it much harder to derive.

Change-Id: I796ef233d470c01f606bd9929820c01ece1f585a
Reviewed-on: https://go-review.googlesource.com/9176Reviewed-by: Rick Hudson <rlh@golang.org>

The trigger controller computes GC CPU utilization by dividing by the
wall-clock time that's passed since concurrent mark began. Since this
delta is nanoseconds it's borderline impossible for it to be zero, but
if it is zero we'll currently divide by zero. Be robust to this
possibility by ignoring the utilization in the error term if no time
has elapsed.

Change-Id: I93dfc9e84735682af3e637f6538d1e7602634f09
Reviewed-on: https://go-review.googlesource.com/9175Reviewed-by: Rick Hudson <rlh@golang.org>

To make the gcprog for global data containing variables of types defined in other shared
libraries, we need to know a lot about those types. So read the value of any symbol with
a name starting with "type.". If a type uses a mask, the name of the symbol defining the
mask unfortunately cannot be predicted from the type name so I have to keep track of the
addresses of every such symbol and associate them with the type symbols after the fact.

I'm not very happy about this change, but something like this is needed and this is as
pleasant as I know how to make it.

Change-Id: I408d831b08b3b31e0610688c41367b23998e975c
Reviewed-on: https://go-review.googlesource.com/8334Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

There were 10 implementations of the trivial bool2int function, 9 of which
were the only thing in their file.  Remove all of them in favor of one in
cmd/internal/obj.

Change-Id: I9c51d30716239df51186860b9842a5e9b27264d3
Reviewed-on: https://go-review.googlesource.com/9230Reviewed-by: Ian Lance Taylor <iant@golang.org>

since the "precision" parameter means constant arithmetic is not
necessarily exact.

As requested by gri, within go/types, the local import name 'exact'
has been kept, to reduce the diff with the x/tools branch.  This may
be changed later.

Since the go/types.bash script was already obsolete, I added a comment
to this effect.

Tested with all.bash.

Change-Id: I45153688d9d8afa8384fb15229b0124c686059b4
Reviewed-on: https://go-review.googlesource.com/9242Reviewed-by: Rob Pike <r@golang.org>

We initially added clone0 to handle the case when G or M don't exist, but
it turns out that we could have just modified clone.  (It also helps that
the function we're invoking in clone0 no longer needs arguments.)

As a side-effect, newosproc0 is now supported on all linux archs.

Change-Id: Ie603af75d8f164310fc16446052d83743961f3ca
Reviewed-on: https://go-review.googlesource.com/9164Reviewed-by: David Crawshaw <crawshaw@golang.org>

Added a prec parameter to MakeFromLiteral (which currently must
always be 0). This will permit go/types to provide an upper limit
for the precision of constant values, eventually. Overflows can be
returned with a special Overflow value (very much like the current
Unknown values).

This is a minimal change that should prevent the need for future
backward-incompatible API changes.

Change-Id: I6c9390d7cc4810375e26c53ed3bde5a383392330
Reviewed-on: https://go-review.googlesource.com/9168
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

In the brief window between getConn and persistConn.roundTrip,
a cancel could end up going missing.

Fix by making it possible to inspect if a cancel function was cleared
and checking if we were canceled before entering roundTrip.

Fixes #10511

Change-Id: If6513e63fbc2edb703e36d6356ccc95a1dc33144
Reviewed-on: https://go-review.googlesource.com/9181Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Previously all errors were 404 errors, even if the real error had
nothing to do with a file being non-existent.

Fixes #10283

Change-Id: I5b08b471a9064c347510cfcf8557373704eef7c0
Reviewed-on: https://go-review.googlesource.com/9200Reviewed-by: Daniel Morsing <daniel.morsing@gmail.com>

There used to be a small window where if a server declared it would do
a keep-alive connection but then actually closed the connection before
the roundTrip goroutine scheduled after being sent a response from the
readLoop goroutine, then the readLoop goroutine would loop around and
block forever reading from a channel because the numExpectedResponses
accounting was done too late.

Fixes #10457

Change-Id: Icbae937ffe83c792c295b7f4fb929c6a24a4f759
Reviewed-on: https://go-review.googlesource.com/9169Reviewed-by: Daniel Morsing <daniel.morsing@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>