Currently the benchmarks lie to testing package by doing O(N)
work under StopTimer. And that hidden O(N) actually consitutes
the bulk of benchmark work (e.g includes GC per iteration).
This behavior accounts for windows-amd64-race builder hangs.

Before:
BenchmarkReaderCopyOptimal-4	 1000000	      1861 ns/op
BenchmarkReaderCopyUnoptimal-4	  500000	      3327 ns/op
BenchmarkReaderCopyNoWriteTo-4	   50000	     34549 ns/op
BenchmarkWriterCopyOptimal-4	  100000	     16849 ns/op
BenchmarkWriterCopyUnoptimal-4	  500000	      3126 ns/op
BenchmarkWriterCopyNoReadFrom-4	   50000	     34609 ns/op
ok  	bufio	65.273s

After:
BenchmarkReaderCopyOptimal-4	10000000	       172 ns/op
BenchmarkReaderCopyUnoptimal-4	10000000	       267 ns/op
BenchmarkReaderCopyNoWriteTo-4	  100000	     22905 ns/op
BenchmarkWriterCopyOptimal-4	10000000	       170 ns/op
BenchmarkWriterCopyUnoptimal-4	10000000	       226 ns/op
BenchmarkWriterCopyNoReadFrom-4	  100000	     20575 ns/op
ok  	bufio	14.074s

Note the change in total time.

LGTM=alex.brainman, rsc
R=golang-codereviews, alex.brainman, rsc
CC=golang-codereviews
https://golang.org/cl/51360046

The R= is populated by Rietveld, so it's basically
anyone who replied to the CL. The LGTM= is meant
to record who actually signed off on the CL.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/55390043

Breaks darwin and freebsd.

««« original CL description
runtime: increase page size to 8K
Tcmalloc uses 8K, 32K and 64K pages, and in custom setups 256K pages.
Only Chromium uses 4K pages today (in "slow but small" configuration).
The general tendency is to increase page size, because it reduces
metadata size and DTLB pressure.
This change reduces GC pause by ~10% and slightly improves other metrics.

json-1
allocated                 8037492      8038689      +0.01%
allocs                     105762       105573      -0.18%
cputime                 158400000    155800000      -1.64%
gc-pause-one              4412234      4135702      -6.27%
gc-pause-total            2647340      2398707      -9.39%
rss                      54923264     54525952      -0.72%
sys-gc                    3952624      3928048      -0.62%
sys-heap                 46399488     46006272      -0.85%
sys-other                 5597504      5290304      -5.49%
sys-stack                  393216       393216      +0.00%
sys-total                56342832     55617840      -1.29%
time                    158478890    156046916      -1.53%
virtual-mem             256548864    256593920      +0.02%

garbage-1
allocated                 2991113      2986259      -0.16%
allocs                      62844        62652      -0.31%
cputime                  16330000     15860000      -2.88%
gc-pause-one            789108229    725555211      -8.05%
gc-pause-total            3945541      3627776      -8.05%
rss                    1143660544   1132253184      -1.00%
sys-gc                   65609600     65806208      +0.30%
sys-heap               1032388608   1035599872      +0.31%
sys-other                37501632     22777664     -39.26%
sys-stack                 8650752      8781824      +1.52%
sys-total              1144150592   1132965568      -0.98%
time                     16364602     15891994      -2.89%
virtual-mem            1327296512   1313746944      -1.02%

R=golang-codereviews, dave, khr, rsc, khr
CC=golang-codereviews
https://golang.org/cl/45770044
»»»

R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/56060043

Tcmalloc uses 8K, 32K and 64K pages, and in custom setups 256K pages.
Only Chromium uses 4K pages today (in "slow but small" configuration).
The general tendency is to increase page size, because it reduces
metadata size and DTLB pressure.
This change reduces GC pause by ~10% and slightly improves other metrics.

json-1
allocated                 8037492      8038689      +0.01%
allocs                     105762       105573      -0.18%
cputime                 158400000    155800000      -1.64%
gc-pause-one              4412234      4135702      -6.27%
gc-pause-total            2647340      2398707      -9.39%
rss                      54923264     54525952      -0.72%
sys-gc                    3952624      3928048      -0.62%
sys-heap                 46399488     46006272      -0.85%
sys-other                 5597504      5290304      -5.49%
sys-stack                  393216       393216      +0.00%
sys-total                56342832     55617840      -1.29%
time                    158478890    156046916      -1.53%
virtual-mem             256548864    256593920      +0.02%

garbage-1
allocated                 2991113      2986259      -0.16%
allocs                      62844        62652      -0.31%
cputime                  16330000     15860000      -2.88%
gc-pause-one            789108229    725555211      -8.05%
gc-pause-total            3945541      3627776      -8.05%
rss                    1143660544   1132253184      -1.00%
sys-gc                   65609600     65806208      +0.30%
sys-heap               1032388608   1035599872      +0.31%
sys-other                37501632     22777664     -39.26%
sys-stack                 8650752      8781824      +1.52%
sys-total              1144150592   1132965568      -0.98%
time                     16364602     15891994      -2.89%
virtual-mem            1327296512   1313746944      -1.02%

R=golang-codereviews, dave, khr, rsc, khr
CC=golang-codereviews
https://golang.org/cl/45770044

The term "package file" is unclear.

R=iant, dave
CC=golang-codereviews
https://golang.org/cl/54760044

Adam (agl@) had already done an initial review of this CL in a branch.

Added ClientSessionState to Config which now allows clients to keep state
required to resume a TLS session with a server. A client handshake will try
and use the SessionTicket/MasterSecret in this cached state if the server
acknowledged resumption.

We also added support to cache ClientSessionState object in Config that will
be looked up by server remote address during the handshake.

R=golang-codereviews, agl, rsc, agl, agl, bradfitz, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/15680043

It implements parsing of the header and symbol table for both
32-bit and 64-bit Plan 9 binaries. The nm tool was updated to
use this package.

R=rsc, aram
CC=golang-codereviews
https://golang.org/cl/49970044

The typo was introduced by one of Dmitriy's CLs this morning.
The fix makes the ARM build compile again; it still won't pass
its tests, but one thing at a time.

TBR=dvyukov
CC=golang-codereviews
https://golang.org/cl/55770044

Sorry, too many windows in which to run all.bash.
Fixes build.

TBR=r
CC=golang-codereviews
https://golang.org/cl/55790043

This change include updates to the probeIPv4Stack
and probeIPv6Stack to ensure that one or both
protocols are supported by ip(3).
The addition of fdMutex to netFD fixes the
TestTCPConcurrentAccept failures.
Additional changes add support for keepalive.

R=golang-codereviews, 0intro
CC=golang-codereviews, rsc
https://golang.org/cl/49920048

Fixes #6546.

LGTM=dave, bradfitz, r
R=r, dave, bradfitz
CC=golang-codereviews
https://golang.org/cl/55780043

warning: /usr/go/src/cmd/gc/obj.c:23 format mismatch -10d VLONG, arg 9
warning: /usr/go/src/cmd/gc/plive.c:1680 set and not used: printed
warning: /usr/go/src/cmd/ld/lib.c:332 non-interruptable temporary
warning: /usr/go/src/cmd/ld/lib.c:338 non-interruptable temporary

R=rsc
CC=golang-codereviews
https://golang.org/cl/53820046

R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/55720044

Linux Flock_t, Unix FcntlFlock, and various BSD Termios.

R=golang-codereviews, dsymonds
CC=golang-codereviews
https://golang.org/cl/55460043

Unbreaks the build.

R=golang-codereviews, dsymonds
CC=golang-codereviews
https://golang.org/cl/53820045

R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/55720043

Doesn't really matter for the most part, since the runtime-integrated
network poller uses its own kevent implementation, but for people using
the syscall directly, we should use an unsafe.Pointer for the precise GC
to retain the pointer arguments.

Also push down unsafe.Pointer a bit further in exec_linux.go, not
that there are any GC preemption points in the middle and sys
is still live anyway.

R=golang-codereviews, dvyukov
CC=golang-codereviews, iant
https://golang.org/cl/55520043

Place && at the end of line.
Offset expression continuation.

R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/55380044

Introduces two-phase goroutine parking mechanism -- prepare to park, commit park.
This mechanism does not require backing mutex to protect wait predicate.
Use it in netpoll. See comment in netpoll.goc for details.
This slightly reduces contention between reader, writer and read/write io notifications;
and just eliminates a bunch of mutex operations from hotpaths, thus making then faster.

benchmark                             old ns/op    new ns/op    delta
BenchmarkTCP4ConcurrentReadWrite           2109         1945   -7.78%
BenchmarkTCP4ConcurrentReadWrite-2         1162         1113   -4.22%
BenchmarkTCP4ConcurrentReadWrite-4          798          755   -5.39%
BenchmarkTCP4ConcurrentReadWrite-8          803          748   -6.85%
BenchmarkTCP4Persistent                    9411         9240   -1.82%
BenchmarkTCP4Persistent-2                  5888         5813   -1.27%
BenchmarkTCP4Persistent-4                  4016         3968   -1.20%
BenchmarkTCP4Persistent-8                  3943         3857   -2.18%

R=golang-codereviews, mikioh.mikioh, gobot, iant, rsc
CC=golang-codereviews, khr
https://golang.org/cl/45700043

The new select tests currently fail (the race is not detected).

R=khr
CC=golang-codereviews
https://golang.org/cl/54220043

Helps reduce contention on sched.goidgen.

benchmark                               old ns/op    new ns/op    delta
BenchmarkCreateGoroutines-16                  259          237   -8.49%
BenchmarkCreateGoroutinesParallel-16          127           43  -66.06%

R=golang-codereviews, dave, bradfitz, khr
CC=golang-codereviews, rsc
https://golang.org/cl/46970043

- do not lose profiling signals when we have no mcache (possible for syscalls/cgo)
- do not lose any profiling signals on windows
- fix profiling of cgo programs on windows (they had no m->thread setup)
- properly setup tls in cgo programs on windows
- check _beginthread return value

Fixes #6417.
Fixes #6986.

R=alex.brainman, rsc
CC=golang-codereviews
https://golang.org/cl/44820047

R=rsc, r, 0intro
CC=golang-codereviews
https://golang.org/cl/36060047

Fixes #6295.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/20850043

Fixes #6572.

LGTM=rsc, daniel.morsing, rsc
R=golang-codereviews, bradfitz, minux.ma, iant, rsc, gobot, daniel.morsing
CC=golang-codereviews
https://golang.org/cl/14516055

In particular: setsockopt, getsockopt, bind, connect.

There are probably more.

All platforms cross-compile with make.bash, and all.bash still
pases on linux/amd64.

Update #7169

R=rsc
CC=golang-codereviews
https://golang.org/cl/55410043

Fixes #7152.

R=iant, rsc, gobot
CC=golang-codereviews
https://golang.org/cl/54790044

Now that liblink is compiled into the compilers and assemblers,
it must not refer to the "linkmode", since that is not known until
link time. This CL makes the ARM support no longer use linkmode,
which fixes a bug with cgo binaries that contain their own TLS
variables.

The x86 code must also remove linkmode; that is issue 7164.

Fixes #6992.

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/55160043

Now it should always fail on ARM.
(The fix is on its way too.)

R=iant, r, dave
CC=golang-codereviews
https://golang.org/cl/55140043

Update #7059

R=rsc
CC=golang-codereviews
https://golang.org/cl/55370043

Fixes #7059

R=golang-codereviews, iant, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/53470043

R=golang-codereviews, iant, khr, dvyukov
CC=golang-codereviews
https://golang.org/cl/54160043

Sorry, "hg status" hides .6 files by default.
We should probably fix that.

TBR=iant
CC=golang-codereviews
https://golang.org/cl/55290043

R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/55140044

R=iant
CC=golang-codereviews
https://golang.org/cl/53820043

The AKILL stuff is not ready yet and
was not meant to be in the last CL.

R=iant
CC=golang-codereviews
https://golang.org/cl/55170043

The escape analysis works by tracing assignment paths from
variables that start with pointer type, or addresses of variables
(addresses are always pointers).  It does allow non-pointers
in the path, so that in this code it sees x's value escape into y:

        var x *[10]int
        y := (*int)(unsafe.Pointer(uintptr(unsafe.Pointer(x))+32))

It must allow uintptr in order to see through this kind of
"pointer arithmetic".

It also traces such values if they end up as uintptrs passed to
functions. This used to be important because packages like
encoding/gob passed around uintptrs holding real pointers.

The introduction of precise collection of stacks has forced
code to be more honest about which declared stack variables
hold pointers and which do not. In particular, the garbage
collector no longer sees pointers stored in uintptr variables.
Because of this, packages like encoding/gob have been fixed.

There is not much point in the escape analysis accepting
uintptrs as holding pointers at call boundaries if the garbage
collector does not.

Excluding uintptr-valued arguments brings the escape
analysis in line with the garbage collector and has the
useful side effect of making arguments to syscall.Syscall
not appear to escape.

That is, this CL should yield the same benefits as
CL 45930043 (rolled back in CL 53870043), but it does
so by making uintptrs less special, not more.

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/53940043

R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/53930043

R=golang-codereviews, gobot, rsc
CC=golang-codereviews
https://golang.org/cl/53950043

Many calls to symgrow pass a vlong value.  Change the function
to not implicitly truncate, and to instead give an error if
the value is too large.

R=golang-codereviews, gobot, rsc
CC=golang-codereviews
https://golang.org/cl/54010043