This only triggers on ARMv7+.
If there are important SMP ARMv6 machines we can reconsider.
Makes TestLFStress tests pass and sync/atomic tests not time out
on Apple iPad Mini 3.
Fixes#7977.
Fixes#10189.
Change-Id: Ie424dea3765176a377d39746be9aa8265d11bec4
Reviewed-on: https://go-review.googlesource.com/12950
Reviewed-by: David Crawshaw <crawshaw@golang.org>
There is absolutely no information about how this was failing.
If we reenable the test then at least we can get a build log from
darwin/arm.
There are not even freebsd/arm or netbsd/arm builders,
so not too worried about those. (That is another problem.)
Change-Id: I0e739a4dd2897adbe110aa400d720d8fa02ae65f
Reviewed-on: https://go-review.googlesource.com/12920
Reviewed-by: Russ Cox <rsc@golang.org>
A comment in waitgroup.go describes the following scenario
as the reason to have dynamically created semaphores:
// G1: Add(1)
// G1: go G2()
// G1: Wait() // Context switch after Unlock() and before Semacquire().
// G2: Done() // Release semaphore: sema == 1, waiters == 0. G1 doesn't run yet.
// G3: Wait() // Finds counter == 0, waiters == 0, doesn't block.
// G3: Add(1) // Makes counter == 1, waiters == 0.
// G3: go G4()
// G3: Wait() // G1 still hasn't run, G3 finds sema == 1, unblocked! Bug.
However, the scenario is incorrect:
G3: Add(1) happens concurrently with G1: Wait(),
and so there is no reasonable behavior of the program
(G1: Wait() may or may not wait for G3: Add(1) which
can't be the intended behavior).
With this conclusion we can:
1. Remove dynamic allocation of semaphores.
2. Remove the mutex entirely and instead pack counter and waiters
into single uint64.
This makes the logic significantly simpler, both Add and Wait
do only a single atomic RMW to update the state.
benchmark old ns/op new ns/op delta
BenchmarkWaitGroupUncontended 30.6 32.7 +6.86%
BenchmarkWaitGroupActuallyWait 722 595 -17.59%
BenchmarkWaitGroupActuallyWait-2 396 319 -19.44%
BenchmarkWaitGroupActuallyWait-4 224 183 -18.30%
BenchmarkWaitGroupActuallyWait-8 134 106 -20.90%
benchmark old allocs new allocs delta
BenchmarkWaitGroupActuallyWait 2 1 -50.00%
benchmark old bytes new bytes delta
BenchmarkWaitGroupActuallyWait 48 16 -66.67%
Change-Id: I28911f3243aa16544e99ac8f1f5af31944c7ea3a
Reviewed-on: https://go-review.googlesource.com/4117
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
All of the architectures except ppc64 have only "RET" for the return
mnemonic. ppc64 used to have only "RETURN", but commit cf06ea6
introduced RET as a synonym for RETURN to make ppc64 consistent with
the other architectures. However, that commit was never followed up to
make the code itself consistent by eliminating uses of RETURN.
This commit replaces all uses of RETURN in the ppc64 assembly with
RET.
This was done with
sed -i 's/\<RETURN\>/RET/' **/*_ppc64x.s
plus one manual change to syscall/asm.s.
Change-Id: I3f6c8d2be157df8841d48de988ee43f3e3087995
Reviewed-on: https://go-review.googlesource.com/10672
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
Similar to darwin/arm. This issue is quite worrying and I hope it
can be addressed for Go 1.5.
Change-Id: Ic095281d6a2e9a38a59973f58d464471db5a2edc
Reviewed-on: https://go-review.googlesource.com/8811
Reviewed-by: Minux Ma <minux@golang.org>
Updates #7338.
Change-Id: I859a73543352dbdd13ec05efb23a95aecbcc628a
Reviewed-on: https://go-review.googlesource.com/7164
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Currently sync.Mutex is fully cooperative. That is, once contention is discovered,
the goroutine calls into scheduler. This is suboptimal as the resource can become
free soon after (especially if critical sections are short). Server software
usually runs at ~~50% CPU utilization, that is, switching to other goroutines
is not necessary profitable.
This change adds limited active spinning to sync.Mutex if:
1. running on a multicore machine and
2. GOMAXPROCS>1 and
3. there is at least one other running P and
4. local runq is empty.
As opposed to runtime mutex we don't do passive spinning,
because there can be work on global runq on on other Ps.
benchmark old ns/op new ns/op delta
BenchmarkMutexNoSpin 1271 1272 +0.08%
BenchmarkMutexNoSpin-2 702 683 -2.71%
BenchmarkMutexNoSpin-4 377 372 -1.33%
BenchmarkMutexNoSpin-8 197 190 -3.55%
BenchmarkMutexNoSpin-16 131 122 -6.87%
BenchmarkMutexNoSpin-32 170 164 -3.53%
BenchmarkMutexSpin 4724 4728 +0.08%
BenchmarkMutexSpin-2 2501 2491 -0.40%
BenchmarkMutexSpin-4 1330 1325 -0.38%
BenchmarkMutexSpin-8 684 684 +0.00%
BenchmarkMutexSpin-16 414 372 -10.14%
BenchmarkMutexSpin-32 559 469 -16.10%
BenchmarkMutex 19.1 19.1 +0.00%
BenchmarkMutex-2 81.6 54.3 -33.46%
BenchmarkMutex-4 143 100 -30.07%
BenchmarkMutex-8 154 156 +1.30%
BenchmarkMutex-16 140 159 +13.57%
BenchmarkMutex-32 141 163 +15.60%
BenchmarkMutexSlack 33.3 31.2 -6.31%
BenchmarkMutexSlack-2 122 97.7 -19.92%
BenchmarkMutexSlack-4 168 158 -5.95%
BenchmarkMutexSlack-8 152 158 +3.95%
BenchmarkMutexSlack-16 140 159 +13.57%
BenchmarkMutexSlack-32 146 162 +10.96%
BenchmarkMutexWork 154 154 +0.00%
BenchmarkMutexWork-2 89.2 89.9 +0.78%
BenchmarkMutexWork-4 139 86.1 -38.06%
BenchmarkMutexWork-8 177 162 -8.47%
BenchmarkMutexWork-16 170 173 +1.76%
BenchmarkMutexWork-32 176 176 +0.00%
BenchmarkMutexWorkSlack 160 160 +0.00%
BenchmarkMutexWorkSlack-2 103 99.1 -3.79%
BenchmarkMutexWorkSlack-4 155 148 -4.52%
BenchmarkMutexWorkSlack-8 176 170 -3.41%
BenchmarkMutexWorkSlack-16 170 173 +1.76%
BenchmarkMutexWorkSlack-32 175 176 +0.57%
"No work" benchmarks are not very interesting (BenchmarkMutex and
BenchmarkMutexSlack), as they are absolutely not realistic.
Fixes#8889
Change-Id: I6f14f42af1fa48f73a776fdd11f0af6dd2bb428b
Reviewed-on: https://go-review.googlesource.com/5430
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
Require a name to be specified when referencing the pseudo-stack.
If you want a real stack offset, use the hardware stack pointer (e.g.,
R13 on arm), not SP.
Fix affected assembly files.
Change-Id: If3545f187a43cdda4acc892000038ec25901132a
Reviewed-on: https://go-review.googlesource.com/5120
Run-TryBot: Rob Pike <r@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
Several .s files for ARM had several properties the new assembler will not support.
These include:
- mentioning SP or PC as a hardware register
These are always pseudo-registers except that in some contexts
they're not, and it's confusing because the context should not affect
which register you mean. Change the references to the hardware
registers to be explicit: R13 for SP, R15 for PC.
- constant creation using assignment
The files say a=b when they could instead say #define a b.
There is no reason to have both mechanisms.
- R(0) to refer to R0.
Some macros use this to a great extent. Again, it's easy just to
use a #define to rename a register.
Change-Id: I002335ace8e876c5b63c71c2560533eb835346d2
Reviewed-on: https://go-review.googlesource.com/4822
Reviewed-by: Dave Cheney <dave@cheney.net>
These depend on storing arbitrary integer values using
pointer atomics, and we can't support that anymore.
Change-Id: I8cadd6d462c3eebdbe7078f43fe7c779fa8f52b3
Reviewed-on: https://go-review.googlesource.com/2311
Reviewed-by: Rick Hudson <rlh@golang.org>
Add write barrier to atomic operations manipulating pointers.
In general an atomic write of a pointer word may indicate racy accesses,
so there is no strictly safe way to attempt to keep the shadow copy
in sync with the real one. Instead, mark the shadow copy as not used.
Redirect sync/atomic pointer routines back to the runtime ones,
so that there is only one copy of the write barrier and shadow logic.
In time we might consider doing this for most of the sync/atomic
functions, but for now only the pointer routines need that treatment.
Found with GODEBUG=wbshadow=1 mode.
Eventually that will run automatically, but right now
it still detects other missing write barriers.
Change-Id: I852936b9a111a6cb9079cfaf6bd78b43016c0242
Reviewed-on: https://go-review.googlesource.com/2066
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
When we start work on Gerrit, ppc64 and garbage collection
work will continue in the master branch, not the dev branches.
(We may still use dev branches for other things later, but
these are ready to be merged, and doing it now, before moving
to Git means we don't have to have dev branches working
in the Gerrit workflow on day one.)
TBR=rlh
CC=golang-codereviews
https://golang.org/cl/183140043
This CL implements the many multiword write barriers by calling
writebarrierptr, so that only writebarrierptr needs the actual barrier.
In lieu of an actual barrier, writebarrierptr checks that the value
being copied is not a small non-zero integer. This is enough to
shake out bugs where the barrier is being called when it should not
(for non-pointer values). It also found a few tests in sync/atomic
that were being too clever.
This CL adds a write barrier for the memory moved during the
builtin copy function, which I forgot when inserting barriers for Go 1.4.
This CL re-enables some write barriers that were disabled for Go 1.4.
Those were disabled because it is possible to change the generated
code so that they are unnecessary most of the time, but we have not
changed the generated code yet. For safety they must be enabled.
None of this is terribly efficient. We are aiming for correct first.
LGTM=rlh
R=rlh
CC=golang-codereviews
https://golang.org/cl/168770043
Fix include paths that got moved in the great pkg/ rename. Add
missing runtime/arch_* files for power64. Port changes that
happened on default since branching to
runtime/{asm,atomic,sys_linux}_power64x.s (precise stacks,
calling convention change, various new and deleted functions.
Port struct renaming and fix some bugs in
runtime/defs_linux_power64.h.
LGTM=rsc
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/161450043
This brings dev.power64 up-to-date with the current tip of
default. go_bootstrap is still panicking with a bad defer
when initializing the runtime (even on amd64).
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/152570049
This also removes pkg/runtime/traceback_lr.c, which was ported
to Go in an earlier commit and then moved to
runtime/traceback.go.
Reviewer: rsc@golang.org
rsc: LGTM
Pool memory was only being released during the first GC after the first Put.
Put assumes that p.local != nil means p is on the allPools list.
poolCleanup (called during each GC) removed each pool from allPools
but did not clear p.local, so each pool was cleared by exactly one GC
and then never cleared again.
This bug was introduced late in the Go 1.3 release cycle.
Fixes#8979.
LGTM=rsc
R=golang-codereviews, bradfitz, r, rsc
CC=golang-codereviews, khr
https://golang.org/cl/162980043
Fixes linux builds (_vdso); may fix others.
I can at least cross-compile cmd/go for every
implemented system now.
TBR=iant
CC=golang-codereviews
https://golang.org/cl/142630043
It is left from the time when Value was implemented in assembly.
Now it is implemented in Go and race detector understands Go.
In particular the atomic operations must provide
all necessary synchronization.
LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews, khr, rsc
https://golang.org/cl/145880043
A Value provides an atomic load and store of a consistently typed value.
It's intended to be used with copy-on-write idiom (see the example).
Performance:
BenchmarkValueRead 50000000 21.7 ns/op
BenchmarkValueRead-2 200000000 8.63 ns/op
BenchmarkValueRead-4 300000000 4.33 ns/op
TBR=rsc
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/136710045
The liblink code to insert the FUNCDATA for a stack map
from the Go prototype was not correct for ARM
(different data structure layout).
Also, sync/atomic was missing some Go prototypes
for ARM-specific functions.
TBR=r
CC=golang-codereviews
https://golang.org/cl/143160045
This is a corner case, and one that was even tested, but this
CL changes the behavior to say that f is "complete" even if it panics.
But don't think of it that way, think of it as sync.Once runs
the function only the first time it is called, rather than
repeatedly until a run of the function completes.
Fixes#8118.
LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/137350043
