runtime/internal/sys will hold system-, architecture- and config-
specific constants.
Updates #11647
Change-Id: I6db29c312556087a42e8d2bdd9af40d157c56b54
Reviewed-on: https://go-review.googlesource.com/16817
Reviewed-by: Russ Cox <rsc@golang.org>
Currently traceBuf keeps track of where it is in the trace buffer by
also maintaining a slice that points in to this buffer with an initial
length of 0 and a cap of the length of the array. All writes to this
buffer are done by appending to the slice (as long as the bounds
checks are right, it will never overflow and the append won't allocate
a new slice).
Each of these appends generates a write barrier. As long as we never
overflow the buffer, this write barrier won't fire, but this wreaks
havoc with eliminating write barriers from the tracing code. If we
were to overflow the buffer, this would both allocate and invoke a
write barrier, both things that are dicey at best to do in many of the
contexts tracing happens. It also wastes space in the traceBuf and
leads to more complex code and more complex generated code.
Replace this slice trick with keeping track of a simple array
position.
Updates #10600.
Change-Id: I0a63eecec1992e195449f414ed47653f66318d0e
Reviewed-on: https://go-review.googlesource.com/16814
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
The tracing code is currently called from contexts such as sysmon and
the scheduler where write barriers are not allowed. Unfortunately,
while the common paths through the tracing code do not have write
barriers, many of the less common paths dealing with buffer overflow
and recycling do.
This change replaces all *traceBufs with traceBufPtrs. In the style of
guintptr, etc., the GC does not trace traceBufPtrs and write barriers
do not apply when these pointers are written. Since traceBufs are
allocated from non-GC'd memory and manually managed, this is always
safe.
Updates #10600.
Change-Id: I52b992d36d1b634ebd855c8cde27947ec14f59ba
Reviewed-on: https://go-review.googlesource.com/16812
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
This change breaks out most of the atomics functions in the runtime
into package runtime/internal/atomic. It adds some basic support
in the toolchain for runtime packages, and also modifies linux/arm
atomics to remove the dependency on the runtime's mutex. The mutexes
have been replaced with spinlocks.
all trybots are happy!
In addition to the trybots, I've tested on the darwin/arm64 builder,
on the darwin/arm builder, and on a ppc64le machine.
Change-Id: I6698c8e3cf3834f55ce5824059f44d00dc8e3c2f
Reviewed-on: https://go-review.googlesource.com/14204
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This moves all of GC initialization, sweep termination, and the
transition to concurrent marking in to the off->mark transition
function. This means it's now handled on the goroutine that detected
the state exit condition.
As a result, malloc no longer needs to Gosched() at the beginning of
the GC cycle to prevent over-allocation while the GC is starting up
because it will now *help* the GC to start up. The Gosched hack is
still necessary during GC shutdown (this is easy to test by enabling
gctrace and hitting Ctrl-S to block the gctrace output).
At this point, the GC coordinator still handles later phases. This
requires a small tweak to how we start the GC coordinator. Currently,
starting the GC coordinator is best-effort and may fail if the
coordinator is about to park from the previous cycle but hasn't yet.
We fix this by replacing the park/ready to wake up the coordinator
with a semaphore. This is temporary since the coordinator will be
going away in a few commits.
Updates #11970.
Change-Id: I2c6a11c91e72dfbc59c2d8e7c66146dee9a444fe
Reviewed-on: https://go-review.googlesource.com/16357
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This begins the conversion of the centralized GC coordinator to a
decentralized state machine by introducing the internal API that
triggers the first state transition from _GCoff to _GCmark (or
_GCmarktermination).
This change introduces the transition lock, the off->mark transition
condition (which is very similar to shouldtriggergc()), and the
general structure of a state transition. Since we're doing this
conversion in stages, it then falls back to the GC coordinator to
actually execute the cycle. We'll start moving logic out of the GC
coordinator and in to transition functions next.
This fixes a minor bug in gcstoptheworld debug mode where passing the
heap trigger once could trigger multiple STW GCs.
Updates #11970.
Change-Id: I964087dd190a639eb5766398f8e1bbf8b352902f
Reviewed-on: https://go-review.googlesource.com/16355
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
The placement and invocation of traceGoSysCall when using
entersyscallblock() instead of entersyscall() differs enough that the
TestTraceSymbolize test can fail on some platforms.
This change moves the invocation of traceGoSysCall for entersyscall() so
that the same number of "frames to skip" are present in the trace as when
entersyscallblock() is used ensuring system call traces remain identical
regardless of internal implementation choices.
Fixesgolang/go#12056
Change-Id: I8361e91aa3708f5053f98263dfe9feb8c5d1d969
Reviewed-on: https://go-review.googlesource.com/13861
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
The call to hash the trace stack reversed the "seed" and "size"
arguments to memhash and, hence, always called memhash with a 0 size,
which dutifully returned a hash value that depended only on the number
of PCs in the stack and not their values. As a result, all stacks were
put in to a very subset of the 8,192 buckets.
Fix this by passing these arguments in the correct order.
Change-Id: I67cd29312f5615c7ffa23e205008dd72c6b8af62
Reviewed-on: https://go-review.googlesource.com/13613
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Nearly all the flaky failures we've seen in trace tests have been
due to the use of time stamps to determine relative event ordering.
This is tricky for many reasons, including:
- different cores might not have exactly synchronized clocks
- VMs are worse than real hardware
- non-x86 chips have different timer resolution than x86 chips
- on fast systems two events can end up with the same time stamp
Stop trying to make time reliable. It's clearly not going to be for Go 1.5.
Instead, record an explicit event sequence number for ordering.
Using our own counter solves all of the above problems.
The trace still contains time stamps, of course. The sequence number
is just used for ordering.
Should alleviate #10554 somewhat. Then tickDiv can be chosen to
be a useful time unit instead of having to be exact for ordering.
Separating ordering and time stamps lets the trace parser diagnose
systems where the time stamp order and actual order do not match
for one reason or another. This CL adds that check to the end of
trace.Parse, after all other sequence order-based checking.
If that error is found, we skip the test instead of failing it.
Putting the check in trace.Parse means that cmd/trace will pick
up the same check, refusing to display a trace where the time stamps
do not match actual ordering.
Using net/http's BenchmarkClientServerParallel4 on various CPU counts,
not tracing vs tracing:
name old time/op new time/op delta
ClientServerParallel4 50.4µs ± 4% 80.2µs ± 4% +59.06% (p=0.000 n=10+10)
ClientServerParallel4-2 33.1µs ± 7% 57.8µs ± 5% +74.53% (p=0.000 n=10+10)
ClientServerParallel4-4 18.5µs ± 4% 32.6µs ± 3% +75.77% (p=0.000 n=10+10)
ClientServerParallel4-6 12.9µs ± 5% 24.4µs ± 2% +89.33% (p=0.000 n=10+10)
ClientServerParallel4-8 11.4µs ± 6% 21.0µs ± 3% +83.40% (p=0.000 n=10+10)
ClientServerParallel4-12 14.4µs ± 4% 23.8µs ± 4% +65.67% (p=0.000 n=10+10)
Fixes#10512.
Change-Id: I173eecf8191e86feefd728a5aad25bf1bc094b12
Reviewed-on: https://go-review.googlesource.com/12579
Reviewed-by: Austin Clements <austin@google.com>
ae1ea2a moved trace-related functions from runtime/pprof to
runtime/trace, but missed a doc comment and a code comment. Update
these to reflect the move.
Change-Id: I6e1e8861e5ede465c08a2e3f80b976145a8b32d8
Reviewed-on: https://go-review.googlesource.com/12525
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
The one in misc/makerelease/makerelease.go is particularly bad and
probably warrants rotating our keys.
I didn't update old weekly notes, and reverted some changes involving
test code for now, since we're late in the Go 1.5 freeze. Otherwise,
the rest are all auto-generated changes, and all manually reviewed.
Change-Id: Ia2753576ab5d64826a167d259f48a2f50508792d
Reviewed-on: https://go-review.googlesource.com/12048
Reviewed-by: Rob Pike <r@golang.org>
There were two issues.
1. Delayed EvGoSysExit could have been emitted during TraceStart,
while it had not yet emitted EvGoInSyscall.
2. Delayed EvGoSysExit could have been emitted during next tracing session.
Fixes#10476Fixes#11262
Change-Id: Iab68eb31cf38eb6eb6eee427f49c5ca0865a8c64
Reviewed-on: https://go-review.googlesource.com/9132
Reviewed-by: Russ Cox <rsc@golang.org>
There are several steps to stopping and starting the world and
currently they're open-coded in several places. The garbage collector
is the only thing that needs to stop and start the world in a
non-trivial pattern. Replace all other uses with calls to higher-level
functions that implement the entire pattern necessary to stop and
start the world.
This is a pure refectoring and should not change any code semantics.
In the following commits, we'll make changes that are easier to do
with this abstraction in place.
This commit renames the old starttheworld to startTheWorldWithSema.
This is a slight misnomer right now because the callers release
worldsema just before calling this. However, a later commit will swap
these and I don't want to think of another name in the mean time.
Change-Id: I5dc97f87b44fb98963c49c777d7053653974c911
Reviewed-on: https://go-review.googlesource.com/10154
Reviewed-by: Russ Cox <rsc@golang.org>
This CL revises CL 7504 to use explicitly uintptr types for the
struct fields that are going to be updated sometimes without
write barriers. The result is that the fields are now updated *always*
without write barriers.
This approach has two important properties:
1) Now the GC never looks at the field, so if the missing reference
could cause a problem, it will do so all the time, not just when the
write barrier is missed at just the right moment.
2) Now a write barrier never happens for the field, avoiding the
(correct) detection of inconsistent write barriers when GODEBUG=wbshadow=1.
Change-Id: Iebd3962c727c0046495cc08914a8dc0808460e0e
Reviewed-on: https://go-review.googlesource.com/9019
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Currently there are two main consumers of memstats.heap_alloc:
updatememstats (aka ReadMemStats) and shouldtriggergc.
updatememstats recomputes heap_alloc from the ground up, so we don't
need to keep heap_alloc up to date for it. shouldtriggergc wants to
know how many bytes were marked by the previous GC plus how many bytes
have been allocated since then, but this *isn't* what heap_alloc
tracks. heap_alloc also includes objects that are not marked and
haven't yet been swept.
Introduce a new memstat called heap_live that actually tracks what
shouldtriggergc wants to know and stop keeping heap_alloc up to date.
Unlike heap_alloc, heap_live follows a simple sawtooth that drops
during each mark termination and increases monotonically between GCs.
heap_alloc, on the other hand, has much more complicated behavior: it
may drop during sweep termination, slowly decreases from background
sweeping between GCs, is roughly unaffected by allocation as long as
there are unswept spans (because we sweep and allocate at the same
rate), and may go up after background sweeping is done depending on
the GC trigger.
heap_live simplifies computing next_gc and using it to figure out when
to trigger garbage collection. Currently, we guess next_gc at the end
of a cycle and update it as we sweep and get a better idea of how much
heap was marked. Now, since we're directly tracking how much heap is
marked, we can directly compute next_gc.
This also corrects bugs that could cause us to trigger GC early.
Currently, in any case where sweep termination actually finds spans to
sweep, heap_alloc is an overestimation of live heap, so we'll trigger
GC too early. heap_live, on the other hand, is unaffected by sweeping.
Change-Id: I1f96807b6ed60d4156e8173a8e68745ffc742388
Reviewed-on: https://go-review.googlesource.com/8389
Reviewed-by: Russ Cox <rsc@golang.org>
Channels and sync.Mutex'es allow another goroutine to acquire resource
ahead of an unblocked goroutine. This is good for performance, but
leads to futile wakeups (the unblocked goroutine needs to block again).
Futile wakeups caused user confusion during the very first evaluation
of tracing functionality on a real server (a goroutine as if acquires a mutex
in a loop, while there is no loop in user code).
This change detects futile wakeups on channels and emits a special event
to denote the fact. Later parser finds entire wakeup sequences
(unblock->start->block) and removes them.
sync.Mutex will be supported in a separate change.
Change-Id: Iaaaee9d5c0921afc62b449a97447445030ac19d3
Reviewed-on: https://go-review.googlesource.com/7380
Reviewed-by: Keith Randall <khr@golang.org>
Augment ProcStart events with OS thread id.
This helps in scheduler locality analysis.
Change-Id: I93fea75d3072cf68de66110d0b59d07101badcb5
Reviewed-on: https://go-review.googlesource.com/7302
Reviewed-by: Keith Randall <khr@golang.org>
Stip uninteresting bottom and top frames from trace stacks.
This makes both binary and json trace files smaller,
and also makes stacks shorter and more readable in the viewer.
Change-Id: Ib9c80ccc280504f0e235f867f53f1d2652c41583
Reviewed-on: https://go-review.googlesource.com/5523
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
This makes Go's CPU profiling code somewhat more idiomatic; e.g.,
using := instead of forward declaring variables, using "int" for
element counts instead of "uintptr", and slices instead of C-style
pointer+length. This makes the code easier to read and eliminates a
lot of type conversion clutter.
Additionally, in sigprof we can collect just maxCPUProfStack stack
frames, as cpuprof won't use more than that anyway.
Change-Id: I0235b5ae552191bcbb453b14add6d8c01381bd06
Reviewed-on: https://go-review.googlesource.com/6072
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Trace command allows to visualize and analyze traces.
Run as:
$ go tool trace binary trace.file
The commands opens web browser with the main page,
which contains links for trace visualization,
blocking profiler, network IO profiler and per-goroutine
traces.
Also move trace parser from runtime/pprof/trace_parser_test.go
to internal/trace/parser.go, so that it can be shared between
tests and the command.
Change-Id: Ic97ed59ad6e4c7e1dc9eca5e979701a2b4aed7cf
Reviewed-on: https://go-review.googlesource.com/3601
Reviewed-by: Andrew Gerrand <adg@golang.org>
Currently race detector produces the following reports on pprof tests:
WARNING: DATA RACE
Read by goroutine 4:
runtime/pprof_test.TestTraceStartStop()
src/runtime/pprof/trace_test.go:38 +0x1da
testing.tRunner()
src/testing/testing.go:448 +0x13a
Previous write by goroutine 5:
bytes.(*Buffer).grow()
src/bytes/buffer.go:102 +0x190
bytes.(*Buffer).Write()
src/bytes/buffer.go:127 +0x75
runtime/pprof.func·002()
src/runtime/pprof/pprof.go:633 +0xae
Trace writer goroutine synchronizes with StopTrace
using trace.shutdownSema runtime semaphore.
But race detector does not see that synchronization
and so produces false reports.
Teach race detector about the synchronization.
Change-Id: I1219817325d4e16b423f29a0cbee94c929793881
Reviewed-on: https://go-review.googlesource.com/3746
Reviewed-by: Russ Cox <rsc@golang.org>
m.gcing has become overloaded to mean "don't preempt this g" in
general. Once the garbage collector is preemptible, the one thing it
*won't* mean is that we're in the garbage collector.
So, rename gcing to "preemptoff" and make it a string giving a reason
that preemption is disabled. gcing was never set to anything but 0 or
1, so we don't have to worry about there being a stack of reasons.
Change-Id: I4337c29e8e942e7aa4f106fc29597e1b5de4ef46
Reviewed-on: https://go-review.googlesource.com/3660
Reviewed-by: Russ Cox <rsc@golang.org>
Austin Clements
Michael Matloob
Shawn Walker-Salas
Russ Cox
Brad Fitzpatrick
Dmitry Vyukov
Shenghou Ma
Matthew Dempsky