Currently it's possible that a goroutine
that periodically executes non-blocking
cgo/syscalls is never preempted.
This change splits scheduler and syscall
ticks to prevent such situation.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12658045
The original plan was to collect allocation stacks
for all memory blocks. But it was never implemented
and it's not in near plans and it's unclear how to do it at all.
R=golang-dev, dave, bradfitz
CC=golang-dev
https://golang.org/cl/12724044
The mutex, fdMutex, handles locking and lifetime of sysfd,
and serializes Read and Write methods.
This allows to strip 2 sync.Mutex.Lock calls,
2 sync.Mutex.Unlock calls, 1 defer and some amount
of misc overhead from every network operation.
On linux/amd64, Intel E5-2690:
benchmark old ns/op new ns/op delta
BenchmarkTCP4Persistent 9595 9454 -1.47%
BenchmarkTCP4Persistent-2 8978 8772 -2.29%
BenchmarkTCP4ConcurrentReadWrite 4900 4625 -5.61%
BenchmarkTCP4ConcurrentReadWrite-2 2603 2500 -3.96%
In general it strips 70-500 ns from every network operation depending
on processor model. On my relatively new E5-2690 it accounts to ~5%
of network op cost.
Fixes#6074.
R=golang-dev, bradfitz, alex.brainman, iant, mikioh.mikioh
CC=golang-dev
https://golang.org/cl/12418043
Introduce freezetheworld function that is a best-effort attempt to stop any concurrently running goroutines. Call it during crash.
Fixes#5873.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12054044
GetQueuedCompletionStatusEx allows to dequeue a batch of completion
notifications, which is more efficient than dequeueing one by one.
benchmark old ns/op new ns/op delta
BenchmarkClientServerParallel4 100605 90945 -9.60%
BenchmarkClientServerParallel4-2 90225 74504 -17.42%
R=golang-dev, alex.brainman
CC=golang-dev
https://golang.org/cl/12436044
Updates #6046.
This CL just does maxstring and concatstring. There are other functions
to fix but doing them a few at a time will help isolate any (unlikely)
breakages these changes bring up in architectures I can't test
myself.
R=golang-dev, dave, iant
CC=golang-dev
https://golang.org/cl/12519044
Update #6046.
This CL just does findnull and findnullw. There are other functions
to fix but doing them a few at a time will help isolate any (unlikely)
breakages these changes bring up in architectures I can't test
myself.
R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/12520043
gcpc/gcsp are used by GC in similar situation.
gcpc/gcsp are also more stable than gp->sched,
because gp->sched is mutated by entersyscall/exitsyscall
in morestack and mcall. So it has higher chances of being inconsistent.
Also, rename gcpc/gcsp to syscallpc/syscallsp.
This is the same as reverted change 12250043
with save marked as textflag 7.
The problem was that if save calls morestack,
then subsequent lessstack spoils g->sched.pc/sp.
And that bad values were remembered in g->syscallpc/sp.
Entersyscallblock had the same problem,
but it was never triggered to date.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12478043
This means that pprof will no longer report profiles on OS X.
That's unfortunate, but the profiles were often wrong and, worse,
it was difficult to tell whether the profile was wrong or not.
The workarounds were making the scheduler more complex,
possibly caused a deadlock (see issue 5519), and did not actually
deliver reliable results.
It may be possible for adventurous users to apply a patch to
their kernels to get working results, or perhaps having no results
will encourage someone to do the work of creating a profiling
thread like on Windows. Issue 6047 has details.
Fixes#5519.
Fixes#6047.
R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/12429045
Break all 386 builders.
««« original CL description
runtime: use gcpc/gcsp during traceback of goroutines in syscalls
gcpc/gcsp are used by GC in similar situation.
gcpc/gcsp are also more stable than gp->sched,
because gp->sched is mutated by entersyscall/exitsyscall
in morestack and mcall. So it has higher chances of being inconsistent.
Also, rename gcpc/gcsp to syscallpc/syscallsp.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12250043
»»»
R=rsc
CC=golang-dev
https://golang.org/cl/12424045
It was needed for the old scheduler,
because there temporary could be more threads than gomaxprocs.
In the new scheduler gomaxprocs is always respected.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12438043
gcpc/gcsp are used by GC in similar situation.
gcpc/gcsp are also more stable than gp->sched,
because gp->sched is mutated by entersyscall/exitsyscall
in morestack and mcall. So it has higher chances of being inconsistent.
Also, rename gcpc/gcsp to syscallpc/syscallsp.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12250043
This allows to at least determine goroutine "identity".
Now it looks like:
goroutine 12 [running]:
goroutine running on other thread; stack unavailable
created by testing.RunTests
src/pkg/testing/testing.go:440 +0x88e
R=golang-dev, r, rsc
CC=golang-dev
https://golang.org/cl/12248043
Split stack checks (morestack) corrupt g->sched,
but g->sched must be preserved consistent for GC/traceback.
The change implements runtime.notetsleepg function,
which does entersyscall/exitsyscall and is carefully arranged
to not call any split functions in between.
R=rsc
CC=golang-dev
https://golang.org/cl/11575044
notetsleepg is the same as notetsleep, but is called on user g.
It includes entersyscall/exitsyscall and will help to avoid
split stack functions in syscall status.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/11681043
This CL introduces a FUNCDATA number for runtime-specific
garbage collection metadata, changes the C and Go compilers
to emit that metadata, and changes the runtime to expect it.
The old pseudo-instructions that carried this information
are gone, as is the linker code to process them.
R=golang-dev, dvyukov, cshapiro
CC=golang-dev
https://golang.org/cl/11406044
whose argument size is unknown (C vararg functions, and
assembly code without an explicit specification).
We used to use 0 to mean "unknown" and 1 to mean "zero".
Now we use ArgsSizeUnknown (0x80000000) to mean "unknown".
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/11590043
Currently preemption signal g->stackguard0==StackPreempt
can be lost if it is received when preemption is disabled
(e.g. m->lock!=0). This change duplicates the preemption
signal in g->preempt and restores g->stackguard0
when preemption is enabled.
Update #543.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10792043
With this CL, I believe the runtime always knows
the frame size during the gc walk. There is no fallback
to "assume entire stack frame of caller" anymore.
R=golang-dev, khr, cshapiro, dvyukov
CC=golang-dev
https://golang.org/cl/11374044
Design at http://golang.org/s/go12symtab.
This enables some cleanup of the garbage collector metadata
that will be done in future CLs.
This CL does not move the old symtab and pclntab back into
an unmapped section of the file. That's a bit tricky and will be
done separately.
Fixes#4020.
R=golang-dev, dave, cshapiro, iant, r
CC=golang-dev, nigeltao
https://golang.org/cl/11085043
The current cas64 definition hard-codes the x86 behavior
of updating *old with the new value when the cas fails.
This is inconsistent with cas32 and casp.
Make it consistent.
This means that the cas64 uses will be epsilon less efficient
than they might be, because they have to do an unnecessary
memory load on x86. But so be it. Code clarity and consistency
is more important.
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/10909045
Currently it replaces GOGCTRACE env var (GODEBUG=gctrace=1).
The plan is to extend it with other type of debug tracing,
e.g. GODEBUG=gctrace=1,schedtrace=100.
R=rsc
CC=bradfitz, daniel.morsing, gobot, golang-dev
https://golang.org/cl/10026045
The last patch for preemptive scheduler,
with this change stoptheworld issues preemption
requests every 100us.
Update #543.
R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://golang.org/cl/10264044
Until now, the goroutine state has been scattered during the
execution of newstack and oldstack. It's all there, and those routines
know how to get back to a working goroutine, but other pieces of
the system, like stack traces, do not. If something does interrupt
the newstack or oldstack execution, the rest of the system can't
understand the goroutine. For example, if newstack decides there
is an overflow and calls throw, the stack tracer wouldn't dump the
goroutine correctly.
For newstack to save a useful state snapshot, it needs to be able
to rewind the PC in the function that triggered the split back to
the beginning of the function. (The PC is a few instructions in, just
after the call to morestack.) To make that possible, we change the
prologues to insert a jmp back to the beginning of the function
after the call to morestack. That is, the prologue used to be roughly:
TEXT myfunc
check for split
jmpcond nosplit
call morestack
nosplit:
sub $xxx, sp
Now an extra instruction is inserted after the call:
TEXT myfunc
start:
check for split
jmpcond nosplit
call morestack
jmp start
nosplit:
sub $xxx, sp
The jmp is not executed directly. It is decoded and simulated by
runtime.rewindmorestack to discover the beginning of the function,
and then the call to morestack returns directly to the start label
instead of to the jump instruction. So logically the jmp is still
executed, just not by the cpu.
The prologue thus repeats in the case of a function that needs a
stack split, but against the cost of the split itself, the extra few
instructions are noise. The repeated prologue has the nice effect of
making a stack split double-check that the new stack is big enough:
if morestack happens to return on a too-small stack, we'll now notice
before corruption happens.
The ability for newstack to rewind to the beginning of the function
should help preemption too. If newstack decides that it was called
for preemption instead of a stack split, it now has the goroutine state
correctly paused if rescheduling is needed, and when the goroutine
can run again, it can return to the start label on its original stack
and re-execute the split check.
Here is an example of a split stack overflow showing the full
trace, without any special cases in the stack printer.
(This one was triggered by making the split check incorrect.)
runtime: newstack framesize=0x0 argsize=0x18 sp=0x6aebd0 stack=[0x6b0000, 0x6b0fa0]
morebuf={pc:0x69f5b sp:0x6aebd8 lr:0x0}
sched={pc:0x68880 sp:0x6aebd0 lr:0x0 ctxt:0x34e700}
runtime: split stack overflow: 0x6aebd0 < 0x6b0000
fatal error: runtime: split stack overflow
goroutine 1 [stack split]:
runtime.mallocgc(0x290, 0x100000000, 0x1)
/Users/rsc/g/go/src/pkg/runtime/zmalloc_darwin_amd64.c:21 fp=0x6aebd8
runtime.new()
/Users/rsc/g/go/src/pkg/runtime/zmalloc_darwin_amd64.c:682 +0x5b fp=0x6aec08
go/build.(*Context).Import(0x5ae340, 0xc210030c71, 0xa, 0xc2100b4380, 0x1b, ...)
/Users/rsc/g/go/src/pkg/go/build/build.go:424 +0x3a fp=0x6b00a0
main.loadImport(0xc210030c71, 0xa, 0xc2100b4380, 0x1b, 0xc2100b42c0, ...)
/Users/rsc/g/go/src/cmd/go/pkg.go:249 +0x371 fp=0x6b01a8
main.(*Package).load(0xc21017c800, 0xc2100b42c0, 0xc2101828c0, 0x0, 0x0, ...)
/Users/rsc/g/go/src/cmd/go/pkg.go:431 +0x2801 fp=0x6b0c98
main.loadPackage(0x369040, 0x7, 0xc2100b42c0, 0x0)
/Users/rsc/g/go/src/cmd/go/pkg.go:709 +0x857 fp=0x6b0f80
----- stack segment boundary -----
main.(*builder).action(0xc2100902a0, 0x0, 0x0, 0xc2100e6c00, 0xc2100e5750, ...)
/Users/rsc/g/go/src/cmd/go/build.go:539 +0x437 fp=0x6b14a0
main.(*builder).action(0xc2100902a0, 0x0, 0x0, 0xc21015b400, 0x2, ...)
/Users/rsc/g/go/src/cmd/go/build.go:528 +0x1d2 fp=0x6b1658
main.(*builder).test(0xc2100902a0, 0xc210092000, 0x0, 0x0, 0xc21008ff60, ...)
/Users/rsc/g/go/src/cmd/go/test.go:622 +0x1b53 fp=0x6b1f68
----- stack segment boundary -----
main.runTest(0x5a6b20, 0xc21000a020, 0x2, 0x2)
/Users/rsc/g/go/src/cmd/go/test.go:366 +0xd09 fp=0x6a5cf0
main.main()
/Users/rsc/g/go/src/cmd/go/main.go:161 +0x4f9 fp=0x6a5f78
runtime.main()
/Users/rsc/g/go/src/pkg/runtime/proc.c:183 +0x92 fp=0x6a5fa0
runtime.goexit()
/Users/rsc/g/go/src/pkg/runtime/proc.c:1266 fp=0x6a5fa8
And here is a seg fault during oldstack:
SIGSEGV: segmentation violation
PC=0x1b2a6
runtime.oldstack()
/Users/rsc/g/go/src/pkg/runtime/stack.c:159 +0x76
runtime.lessstack()
/Users/rsc/g/go/src/pkg/runtime/asm_amd64.s:270 +0x22
goroutine 1 [stack unsplit]:
fmt.(*pp).printArg(0x2102e64e0, 0xe5c80, 0x2102c9220, 0x73, 0x0, ...)
/Users/rsc/g/go/src/pkg/fmt/print.go:818 +0x3d3 fp=0x221031e6f8
fmt.(*pp).doPrintf(0x2102e64e0, 0x12fb20, 0x2, 0x221031eb98, 0x1, ...)
/Users/rsc/g/go/src/pkg/fmt/print.go:1183 +0x15cb fp=0x221031eaf0
fmt.Sprintf(0x12fb20, 0x2, 0x221031eb98, 0x1, 0x1, ...)
/Users/rsc/g/go/src/pkg/fmt/print.go:234 +0x67 fp=0x221031eb40
flag.(*stringValue).String(0x2102c9210, 0x1, 0x0)
/Users/rsc/g/go/src/pkg/flag/flag.go:180 +0xb3 fp=0x221031ebb0
flag.(*FlagSet).Var(0x2102f6000, 0x293d38, 0x2102c9210, 0x143490, 0xa, ...)
/Users/rsc/g/go/src/pkg/flag/flag.go:633 +0x40 fp=0x221031eca0
flag.(*FlagSet).StringVar(0x2102f6000, 0x2102c9210, 0x143490, 0xa, 0x12fa60, ...)
/Users/rsc/g/go/src/pkg/flag/flag.go:550 +0x91 fp=0x221031ece8
flag.(*FlagSet).String(0x2102f6000, 0x143490, 0xa, 0x12fa60, 0x0, ...)
/Users/rsc/g/go/src/pkg/flag/flag.go:563 +0x87 fp=0x221031ed38
flag.String(0x143490, 0xa, 0x12fa60, 0x0, 0x161950, ...)
/Users/rsc/g/go/src/pkg/flag/flag.go:570 +0x6b fp=0x221031ed80
testing.init()
/Users/rsc/g/go/src/pkg/testing/testing.go:-531 +0xbb fp=0x221031edc0
strings_test.init()
/Users/rsc/g/go/src/pkg/strings/strings_test.go:1115 +0x62 fp=0x221031ef70
main.init()
strings/_test/_testmain.go:90 +0x3d fp=0x221031ef78
runtime.main()
/Users/rsc/g/go/src/pkg/runtime/proc.c:180 +0x8a fp=0x221031efa0
runtime.goexit()
/Users/rsc/g/go/src/pkg/runtime/proc.c:1269 fp=0x221031efa8
goroutine 2 [runnable]:
runtime.MHeap_Scavenger()
/Users/rsc/g/go/src/pkg/runtime/mheap.c:438
runtime.goexit()
/Users/rsc/g/go/src/pkg/runtime/proc.c:1269
created by runtime.main
/Users/rsc/g/go/src/pkg/runtime/proc.c:166
rax 0x23ccc0
rbx 0x23ccc0
rcx 0x0
rdx 0x38
rdi 0x2102c0170
rsi 0x221032cfe0
rbp 0x221032cfa0
rsp 0x7fff5fbff5b0
r8 0x2102c0120
r9 0x221032cfa0
r10 0x221032c000
r11 0x104ce8
r12 0xe5c80
r13 0x1be82baac718
r14 0x13091135f7d69200
r15 0x0
rip 0x1b2a6
rflags 0x10246
cs 0x2b
fs 0x0
gs 0x0
Fixes#5723.
R=r, dvyukov, go.peter.90, dave, iant
CC=golang-dev
https://golang.org/cl/10360048
It was used to request large stack segment for GC
when it was running not on g0.
Now GC is running on g0 with large stack,
and it is not needed anymore.
R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/10242045
Add gostartcall and gostartcallfn.
The old gogocall = gostartcall + gogo.
The old gogocallfn = gostartcallfn + gogo.
R=dvyukov, minux.ma
CC=golang-dev
https://golang.org/cl/10036044
The garbage collection routine addframeroots is duplicating
logic in the traceback routine that calls it, sometimes correctly,
sometimes incorrectly, sometimes incompletely.
Pass necessary information to addframeroots instead of
deriving it anew.
Should make addframeroots significantly more robust.
It's certainly smaller.
Also try to standardize on uintptr for saved pc, sp values.
Will make CL 10036044 trivial.
R=golang-dev, dave, dvyukov
CC=golang-dev
https://golang.org/cl/10169045
This is part of preemptive scheduler.
stackguard0 is checked in split stack checks and can be set to StackPreempt.
stackguard is not set to StackPreempt (holds the original value).
R=golang-dev, daniel.morsing, iant
CC=golang-dev
https://golang.org/cl/9875043
This is needed for preemptive scheduler, because during
stoptheworld we want to wait with timeout and re-preempt
M's on timeout.
R=golang-dev, remyoudompheng, iant
CC=golang-dev
https://golang.org/cl/9375043
With this change the compiler emits a bitmap for each function
covering its stack frame arguments area. If an argument word
is known to contain a pointer, a bit is set. The garbage
collector reads this information when scanning the stack by
frames and uses it to ignores locations known to not contain a
pointer.
R=golang-dev, bradfitz, daniel.morsing, dvyukov, khr, khr, iant, cshapiro
CC=golang-dev
https://golang.org/cl/9223046
When cgo is used, runtime creates an additional M to handle callbacks on threads not created by Go.
This effectively disabled deadlock detection, which is a right thing, because Go program can be blocked
and only serve callbacks on external threads.
This also disables deadlock detection under race detector, because it happens to use cgo.
With this change the additional M is created lazily on first cgo call. So deadlock detector
works for programs that import "C", "net" or "net/http/pprof" but do not use them in fact.
Also fixes deadlock detector under race detector.
It should be fine to create the M later, because C code can not call into Go before first cgo call,
because C code does not know when Go initialization has completed. So a Go program need to call into C
first either to create an external thread, or notify a thread created in global ctor that Go
initialization has completed.
Fixes#4973.
Fixes#5475.
R=golang-dev, minux.ma, iant
CC=golang-dev
https://golang.org/cl/9303046
This makes it an unsafe.Pointer in Go so the garbage collector
will treat it as a pointer to untyped data, not a pointer to
bytes.
R=golang-dev, dvyukov
CC=golang-dev
https://golang.org/cl/8286045
