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Change reflect to call a new function to get the compiled type descriptors,
returning the type pointers directly rather than the type offsets.
We have to keep the existing reflect.typelinks for third party
packages that break the rules and call it directly using linkname.
Change-Id: I476efb6bd7836a7a5f396c97bbe4b2c1a2428990
Reviewed-on: https://go-review.googlesource.com/c/go/+/729502
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Antonio Camacho <antoniocho444@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
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https://go.dev/cl/742580 updated the goroutine label format in
tracebacks to only quote the values under some circumstances, and use a
more broadly acceptable format. Flip the GODEBUG=tracebacklabels default
for go 1.27+ modules.
Notably, tracebacklabels is marked as Opaque to avoid some diciness in
maintaining a usage metric in signal handlers, etc. (where mutex
acquisition may be problematic)
Also, update the go 1.27 release notes to call out the new feature.
Updates #76349
Change-Id: Iedd3f6b17d83e99da20365b952a565022d20ff13
Reviewed-on: https://go-review.googlesource.com/c/go/+/751580
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Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
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On AIX the runtime adjusts the GCData field in getGCMaskOnDemand
to account for the AIX dynamic loader moving the data section.
That works fine for statically generated types,
but it breaks user generated types. The user generated type
will have a normal, correct, pointer, and adjusting the pointer
will make it point elsewhere.
This all happens to work OK when doing an external link,
because in that case we do have dynamic relocs and there is no adjustment.
But it fails with an internal link.
This CL fixes the problem by applying a reverse adjustment to
user generated types, so that the adjustment winds up with the
original pointer value.
Change-Id: Ibf3199b9ffb36e79af134fbed41db2853297de74
Reviewed-on: https://go-review.googlesource.com/c/go/+/740800
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
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Reviewed-by: Roland Shoemaker <roland@golang.org>
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Instead of adding a typelinks section to a Go binary,
mark the start and end of the typelinked type descriptors.
The runtime can then step through the descriptors to find them all,
rather than relying on the extra linker-generated offset list.
The runtime steps through the type descriptors lazily,
as many Go programs don't need the typelinks list at all.
This reduces the size of cmd/go by 15K bytes, which isn't much
but it's not nothing.
A future CL will change the reflect package to use the type pointers
directly rather than converting to offsets and then back to type pointers.
For #6853
Change-Id: Id0af4ce81c5b1cea899fc92b6ff9d2db8ce4c267
Reviewed-on: https://go-review.googlesource.com/c/go/+/724261
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
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Auto-Submit: Ian Lance Taylor <iant@golang.org>
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Copy LabelSet to an internal package as label.Set, and include (escaped)
labels within goroutine stack dumps.
Labels are added to the goroutine header as quoted key:value pairs, so
the line may get long if there are a lot of labels.
To handle escaping, we add a printescaped function to the
runtime and hook it up to the print function in the compiler with a new
runtime.quoted type that's a sibling to runtime.hex. (in fact, we
leverage some of the machinery from printhex to generate escape
sequences).
The escaping can be improved for printable runes outside basic ASCII
(particularly for languages using non-latin stripts). Additionally,
invalid UTF-8 can be improved.
So we can experiment with the output format make this opt-in via a
a new tracebacklabels GODEBUG var.
Updates #23458
Updates #76349
Change-Id: I08e78a40c55839a809236fff593ef2090c13c036
Reviewed-on: https://go-review.googlesource.com/c/go/+/694119
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Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
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The documentation for GOTRACEBACK says that "single" is the default
where the stack trace for only a single routine is printed except
that it prints all stack traces if:
there is no current goroutine or
the failure is internal to the run-time.
In the runtime, there are two types of panics:
throwTypeUser and throwTypeRuntime.
The latter more clearly corresponds to a
"failure [that] is internal to the run-time",
while the former corresponds to a
problem trigger due to a user mistake.
Thus, a user-triggered panic (e.g., concurrent map access)
should not result in a dump of all stack traces.
Fixes #68019
Change-Id: I9b02f82535ddb9fd666f7158e2e4ee10f235646a
Reviewed-on: https://go-review.googlesource.com/c/go/+/649535
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Now that the compiler handles constant 64-bit divisions
without function calls on 32-bit systems, we no longer need
to maintain and test a bad custom implementation of 64-bit division.
Change-Id: If28807ad4f86507267ae69bc8f0b09ec18e98b66
Reviewed-on: https://go-review.googlesource.com/c/go/+/716463
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Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
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Replaced by internal/strconv.
Change-Id: I0656a9ad5075e60339e963fbae7d194d2f3e16be
Reviewed-on: https://go-review.googlesource.com/c/go/+/716001
Reviewed-by: David Chase <drchase@google.com>
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This is necessary specifically to set the value of `debug.decoratemappings`
sufficiently early in the startup sequence that all memory ranges allocated
can be named appropriately using the new Linux-specific naming API
introduced in #71546.
Example output (on ARM64):
https://gist.github.com/9muir/3667654b9c3f52e8be92756219371672
Fixes: #75324
Change-Id: Ic0b16233f54a45adef1660c4d0df59af2f5af86a
Reviewed-on: https://go-review.googlesource.com/c/go/+/703476
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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This CL adds two related features enabled by default via compatibility
GODEBUGs containermaxprocs and updatemaxprocs.
On Linux, containermaxprocs makes the Go runtime consider cgroup CPU
bandwidth limits (quota/period) when setting GOMAXPROCS. If the cgroup
limit is lower than the number of logical CPUs available, then the
cgroup limit takes precedence.
On all OSes, updatemaxprocs makes the Go runtime periodically
recalculate the default GOMAXPROCS value and update GOMAXPROCS if it has
changed. If GOMAXPROCS is set manually, this update does not occur. This
is intended primarily to detect changes to cgroup limits, but it applies
on all OSes because the CPU affinity mask can change as well.
The runtime only considers the limit in the leaf cgroup (the one that
actually contains the process), caching the CPU limit file
descriptor(s), which are periodically reread for updates. This is a
small departure from the original proposed design. It will not consider
limits of parent cgroups (which may be lower than the leaf), and it will
not detection cgroup migration after process start.
We can consider changing this in the future, but the simpler approach is
less invasive; less risk to packages that have some awareness of runtime
internals. e.g., if the runtime periodically opens new files during
execution, file descriptor leak detection is difficult to implement in a
stable way.
For #73193.
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
Change-Id: I6a6a636c631c1ae577fb8254960377ba91c5dc98
Reviewed-on: https://go-review.googlesource.com/c/go/+/670497
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This change adds support for identifying cleanups and finalizers
attached to tiny blocks to checkfinalizers mode. It also notes a subtle
pitfall, which is that the cleanup arg, if tiny-allocated, could end up
co-located with the object with the cleanup attached! Oops...
For #72949.
Change-Id: Icbe0112f7dcfc63f35c66cf713216796a70121ce
Reviewed-on: https://go-review.googlesource.com/c/go/+/662037
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Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
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This new debug mode detects cleanup/finalizer leaks using checkmark
mode. It runs a partial GC using only specials as roots. If the GC can
find a path from one of these roots back to the object the special is
attached to, then the object might never be reclaimed. (The cycle could
be broken in the future, but it's almost certainly a bug.)
This debug mode is very barebones. It contains no type information and
no stack location for where the finalizer or cleanup was created.
For #72949.
Change-Id: Ibffd64c1380b51f281950e4cfe61f677385d42a5
Reviewed-on: https://go-review.googlesource.com/c/go/+/634599
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
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Moving to a smaller package allows its use in other internal/runtime
packages.
This isn't internal/strconvlite since it can't be used directly by
strconv.
For #73193.
Change-Id: I6a6a636c9c8b3f06b5fd6c07fe9dd5a7a37d1429
Reviewed-on: https://go-review.googlesource.com/c/go/+/672697
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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Go 1.22 promised to remove the setting in a future release once the
semantics of runtime-internal lock contention matched that of
sync.Mutex. That work is done, remove the setting.
Previously reviewed as https://go.dev/cl/585639.
For #66999
Change-Id: I9fe62558ba0ac12824874a0bb1b41efeb7c0853f
Reviewed-on: https://go-review.googlesource.com/c/go/+/668995
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Auto-Submit: Rhys Hiltner <rhys.hiltner@gmail.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
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This adds a new godebug to control whether the runtime applies the
anonymous memory mapping annotations added in https://go.dev/cl/646095.
It is enabled by default.
This has several effects:
* The feature is only enabled by default when the main go.mod has go >=
1.25.
* This feature can be disabled with GODEBUG=decoratemappings=0, or the
equivalents in go.mod or package main. See https://go.dev/doc/godebug.
* As an opaque setting, this option will not appear in runtime/metrics.
* This setting is non-atomic, so it cannot be changed after startup.
I am not 100% sure about my decision for the last two points.
I've made this an opaque setting because it affects every memory mapping
the runtime performs. Thus every mapping would report "non-default
behavior", which doesn't seem useful.
This setting could trivially be atomic and allow changes at run time,
but those changes would only affect future mappings. That seems
confusing and not helpful. On the other hand, going back to annotate or
unannotate every previous mapping when the setting changes is
unwarranted complexity.
For #71546.
Change-Id: I6a6a636c5ad551d76691cba2a6f668d5cff0e352
Reviewed-on: https://go-review.googlesource.com/c/go/+/655895
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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This change fixes GODEBUG=gccheckmark=1 which seems to have bit-rotted.
Because the root jobs weren't being reset, it wasn't doing anything.
Then, it turned out that checkmark mode would queue up noscan objects in
workbufs, which caused it to fail. Then it turned out checkmark mode was
broken with user arenas, since their heap arenas are not registered
anywhere. Then, it turned out that checkmark mode could just not run
properly if the goroutine's preemption flag was set (since
sched.gcwaiting is true during the STW). And lastly, it turned out that
async preemption could cause erroneous checkmark failures.
This change fixes all these issues and adds a simple smoke test to dist
to run the runtime tests under gccheckmark, which exercises all of these
issues.
Fixes #69074.
Fixes #69377.
Fixes #69376.
Change-Id: Iaa0bb7b9e63ed4ba34d222b47510d6292ce168bc
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest
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Reviewed-by: Carlos Amedee <carlos@golang.org>
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Sometimes we've used the 140 suffix (GOFIPS140, crypto/fips140)
and sometimes not (crypto/internal/fips, cmd/go/internal/fips).
Use it always, to avoid having to remember which is which.
Also, there are other FIPS standards, like AES (FIPS 197), SHA-2 (FIPS 180),
and so on, which have nothing to do with FIPS 140. Best to be clear.
For #70123.
Change-Id: I33b29dabd9e8b2703d2af25e428f88bc81c7c307
Reviewed-on: https://go-review.googlesource.com/c/go/+/630115
Reviewed-by: Filippo Valsorda <filippo@golang.org>
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Add a new function, WithDataIndependentTiming, which takes a function as
an argument, and encloses it with calls to set/unset the DIT PSTATE bit
on Arm64.
Since DIT is OS thread-local, for the duration of the execution of
WithDataIndependentTiming, we lock the goroutine to the OS thread, using
LockOSThread. For long running operations, this is likely to not be
performant, but we expect this to be tightly scoped around cryptographic
operations that have bounded execution times.
If locking to the OS thread turns out to be too slow, another option is
to add a bit to the g state indicating if a goroutine has DIT enabled,
and then have the scheduler enable/disable DIT when scheduling a g.
Additionally, we add a new GODEBUG, dataindependenttiming, which allows
setting DIT for an entire program. Running a program with
dataindependenttiming=1 enables DIT for the program during
initialization. In an ideal world PSTATE.DIT would be inherited from
the parent thread, so we'd only need to set it in the main thread and
then all subsequent threads would inherit the value. While this does
happen in the Linux kernel [0], it is not the case for darwin [1].
Rather than add complex logic to only set it on darwin for each new
thread, we just unconditionally set it in mstart1 and cgocallbackg1
regardless of the OS. DIT will already impose some overhead, and the
cost of setting the bit is only ~two instructions (CALL, MSR), so it
should be cheap enough.
Fixes #66450
Updates #49702
[0] https://github.com/torvalds/linux/blob/e8bdb3c8be08c9a3edc0a373c0aa8729355a0705/arch/arm64/kernel/process.c#L373
[1] https://github.com/apple-oss-distributions/xnu/blob/8d741a5de7ff4191bf97d57b9f54c2f6d4a15585/osfmk/arm64/status.c#L1666
Change-Id: I78eda691ff9254b0415f2b54770e5850a0179749
Reviewed-on: https://go-review.googlesource.com/c/go/+/598336
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
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Placed the fipsIndicator field in some 64-bit alignment padding in the g
struct to avoid growing per-goroutine memory requirements on 64-bit
targets.
Fixes #69911
Updates #69536
Change-Id: I176419d0e3814574758cb88a47340a944f405604
Reviewed-on: https://go-review.googlesource.com/c/go/+/620795
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
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frugal no longer uses these methods from next Go version
Fixes #69222
Change-Id: Ie71de0752cabef7d5584d3392d6e5920ba742350
Reviewed-on: https://go-review.googlesource.com/c/go/+/609918
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
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This reverts commit 87e930f7289136fad1310d4b63dd4127e409bac5 (CL 585639)
Reason for revert: This is part of a patch series that changed the
handling of contended lock2/unlock2 calls, reducing the maximum
throughput of contended runtime.mutex values, and causing a performance
regression on applications where that is (or became) the bottleneck.
Updates #66999
Updates #67585
Change-Id: I1e286d2a16d16e4af202cd5dc04b2d9c4ee71b32
Reviewed-on: https://go-review.googlesource.com/c/go/+/589097
Reviewed-by: Than McIntosh <thanm@google.com>
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Add linknames for most modules with ≥50 dependents.
Add linknames for a few other modules that we know
are important but are below 50.
Remove linknames from badlinkname.go that do not merit
inclusion (very small number of dependents).
We can add them back later if the need arises.
Fixes #67401. (For now.)
Change-Id: I1e49fec0292265256044d64b1841d366c4106002
Reviewed-on: https://go-review.googlesource.com/c/go/+/587756
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Bypass: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
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Ignored these linknames which have not worked for a while:
github.com/xtls/xray-core:
context.newCancelCtx removed in CL 463999 (Feb 2023)
github.com/u-root/u-root:
funcPC removed in CL 513837 (Jul 2023)
tinygo.org/x/drivers:
net.useNetdev never existed
For #67401.
Change-Id: I9293f4ef197bb5552b431de8939fa94988a060ce
Reviewed-on: https://go-review.googlesource.com/c/go/+/587576
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
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For #67401.
Change-Id: I3ae93042dffd0683b7e6d6225536ae667749515b
Reviewed-on: https://go-review.googlesource.com/c/go/+/587221
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
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Note that this depends on the revert of CL 581395 to move zeroVal back.
For #67401.
Change-Id: I507c27c2404ad1348aabf1ffa3740e6b1957495b
Reviewed-on: https://go-review.googlesource.com/c/go/+/587217
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For #67401.
Change-Id: I51f5b561ee11eb242e3b1585d591281d0df4fc24
Reviewed-on: https://go-review.googlesource.com/c/go/+/587215
Auto-Submit: Russ Cox <rsc@golang.org>
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Go 1.22 promised to remove the setting in a future release once the
semantics of runtime-internal lock contention matched that of
sync.Mutex. That work is done, remove the setting.
For #66999
Change-Id: I3c4894148385adf2756d8754e44d7317305ad758
Reviewed-on: https://go-review.googlesource.com/c/go/+/585639
Reviewed-by: Carlos Amedee <carlos@golang.org>
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Allow users to decrease the profiling stack depth back to 32 in case
they experience any problems with the new default of 128.
Users may also use this option to increase the depth up to 1024.
Change-Id: Ieaab2513024915a223239278dd97a6e161dde1cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/581917
Reviewed-by: Austin Clements <austin@google.com>
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This change adds expensive alloc/free events to traces, guarded by a
GODEBUG that can be set at run time by mutating the GODEBUG environment
variable. This supersedes the alloc/free trace deleted in a previous CL.
There are two parts to this CL.
The first part is adding a mechanism for exposing experimental events
through the tracer and trace parser. This boils down to a new
ExperimentalEvent event type in the parser API which simply reveals the
raw event data for the event. Each experimental event can also be
associated with "experimental data" which is associated with a
particular generation. This experimental data is just exposed as a bag
of bytes that supplements the experimental events.
In the runtime, this CL organizes experimental events by experiment.
An experiment is defined by a set of experimental events and a single
special batch type. Batches of this special type are exposed through the
parser's API as the aforementioned "experimental data".
The second part of this CL is defining the AllocFree experiment, which
defines 9 new experimental events covering heap object alloc/frees, span
alloc/frees, and goroutine stack alloc/frees. It also generates special
batches that contain a type table: a mapping of IDs to type information.
Change-Id: I965c00e3dcfdf5570f365ff89d0f70d8aeca219c
Reviewed-on: https://go-review.googlesource.com/c/go/+/583377
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allocfreetrace prints all allocations and frees to stderr. It's not
terribly useful because it has a really huge overhead, making it not
feasible to use except for the most trivial programs. A follow-up CL
will replace it with something that is both more thorough and also lower
overhead.
Change-Id: I1d668fee8b6aaef5251a5aea3054ec2444d75eb6
Reviewed-on: https://go-review.googlesource.com/c/go/+/583376
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Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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Currently, the execution tracer may attempt to take a stack trace of a
goroutine whose stack it does not own. For example, if the goroutine is
in _Grunnable or _Gwaiting. This is easily fixed in all cases by simply
moving the emission of GoStop and GoBlock events to before the
casgstatus happens. The goroutine status is what is used to signal stack
ownership, and the GC may shrink a goroutine's stack if it can acquire
the scan bit.
Although this is easily fixed, the interaction here is very subtle,
because stack ownership is only implicit in the goroutine's scan status.
To make this invariant more maintainable and less error-prone in the
future, this change adds a GODEBUG setting that checks, at the point of
taking a stack trace, whether the caller owns the goroutine. This check
is not quite perfect because there's no way for the stack tracing code
to know that the _Gscan bit was acquired by the caller, so for
simplicity it assumes that it was the caller that acquired the scan bit.
In all other cases however, we can check for ownership precisely. At the
very least, this check is sufficient to catch the issue this change is
fixing.
To make sure this debug check doesn't bitrot, it's always enabled during
trace testing. This new mode has actually caught a few other issues
already, so this change fixes them.
One issue that this debug mode caught was that it's not safe to take a
stack trace of a _Gwaiting goroutine that's being unparked.
Another much bigger issue this debug mode caught was the fact that the
execution tracer could try to take a stack trace of a G that was in
_Gwaiting solely to avoid a deadlock in the GC. The execution tracer
already has a partial list of these cases since they're modeled as the
goroutine just executing as normal in the tracer, but this change takes
the list and makes it more formal. In this specific case, we now prevent
the GC from shrinking the stacks of goroutines in this state if tracing
is enabled. The stack traces from these scenarios are too useful to
discard, but there is indeed a race here between the tracer and any
attempt to shrink the stack by the GC.
Change-Id: I019850dabc8cede202fd6dcc0a4b1f16764209fb
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-linux-amd64-longtest-race
Reviewed-on: https://go-review.googlesource.com/c/go/+/573155
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Auto-Submit: Michael Knyszek <mknyszek@google.com>
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For #65355
Change-Id: I65dd090fb99de9b231af2112c5ccb0eb635db2be
Reviewed-on: https://go-review.googlesource.com/c/go/+/560155
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
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Reviewed-by: Ibrahim Bazoka <ibrahimbazoka729@gmail.com>
Auto-Submit: Emmanuel Odeke <emmanuel@orijtech.com>
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From the beginning of Go, the time package has had a gotcha:
if you use a select on <-time.After(1*time.Minute), even if the select
finishes immediately because some other case is ready, the underlying
timer from time.After keeps running until the minute is over. This
pins the timer in the timer heap, which keeps it from being garbage
collected and in extreme cases also slows down timer operations.
The lack of garbage collection is the more important problem.
The docs for After warn against this scenario and suggest using
NewTimer with a call to Stop after the select instead, purely to work
around this garbage collection problem.
Oddly, the docs for NewTimer and NewTicker do not mention this
problem, but they have the same issue: they cannot be collected until
either they are Stopped or, in the case of Timer, the timer expires.
(Tickers repeat, so they never expire.) People have built up a shared
knowledge that timers and tickers need to defer t.Stop even though the
docs do not mention this (it is somewhat implied by the After docs).
This CL fixes the garbage collection problem, so that a timer that is
unreferenced can be GC'ed immediately, even if it is still running.
The approach is to only insert the timer into the heap when some
channel operation is blocked on it; the last channel operation to stop
using the timer takes it back out of the heap. When a timer's channel
is no longer referenced, there are no channel operations blocked on
it, so it's not in the heap, so it can be GC'ed immediately.
This CL adds an undocumented GODEBUG asynctimerchan=1
that will disable the change. The documentation happens in
the CL 568341.
Fixes #8898.
Fixes #61542.
Change-Id: Ieb303b6de1fb3527d3256135151a9e983f3c27e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/512355
Reviewed-by: Austin Clements <austin@google.com>
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Auto-Submit: Russ Cox <rsc@golang.org>
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This commit is aimed at improving the readability and consistency
of the code base. Extraneous newline characters were present after
some return statements, creating unnecessary separation in the code.
Fixes #64610
Change-Id: Ic1b05bf11761c4dff22691c2f1c3755f66d341f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/548316
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
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Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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profileruntimelocks is new in CL 544195, but the name is deceptive. Even
with profileruntimelocks=0, runtime-internal locks are still profiled.
The actual difference is that call stacks are not collected. Instead all
contention is reported at runtime._LostContendedLock.
Rename this setting to runtimecontentionstacks to make its name more
aligned with its behavior.
In addition, for this release the default is profileruntimelocks=0,
meaning that users are fairly likely to encounter
runtime._LostContendedLock. Rename it to
runtime._LostContendedRuntimeLock in an attempt to make it more
intuitive that these are runtime locks, not locks in application code.
For #57071.
Change-Id: I38aac28b2c0852db643d53b1eab3f3bc42a43393
Reviewed-on: https://go-review.googlesource.com/c/go/+/547055
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
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Reviewed-by: Rhys Hiltner <rhys@justin.tv>
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Go 1.21.1 and Go 1.22 have ceased working around an issue with Linux
kernel defaults for transparent huge pages that can result in excessive
memory overheads. (https://bugzilla.kernel.org/show_bug.cgi?id=93111)
Many Linux distributions disable huge pages altogether these days, so
this problem isn't quite as far-reaching as it used to be. Also, the
problem only affects Go programs with very particular memory usage
patterns.
That being said, because the runtime used to actively deal with this
problem (but with some unpredictable behavior), it's preventing users
that don't have a lot of control over their execution environment from
upgrading to Go beyond Go 1.20.
This change adds a GODEBUG to smooth over the transition. The GODEBUG
setting disables transparent huge pages for all heap memory on Linux,
which is much more predictable than restoring the old behavior.
Fixes #64332.
Change-Id: I73b1894337f0f0b1a5a17b90da1221e118e0b145
Reviewed-on: https://go-review.googlesource.com/c/go/+/547475
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
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Add runtime-internal locks to the mutex contention profile.
Store up to one call stack responsible for lock contention on the M,
until it's safe to contribute its value to the mprof table. Try to use
that limited local storage space for a relatively large source of
contention, and attribute any contention in stacks we're not able to
store to a sentinel _LostContendedLock function.
Avoid ballooning lock contention while manipulating the mprof table by
attributing to that sentinel function any lock contention experienced
while reporting lock contention.
Guard collecting real call stacks with GODEBUG=profileruntimelocks=1,
since the available data has mixed semantics; we can easily capture an
M's own wait time, but we'd prefer for the profile entry of each
critical section to describe how long it made the other Ms wait. It's
too late in the Go 1.22 cycle to make the required changes to
futex-based locks. When not enabled, attribute the time to the sentinel
function instead.
Fixes #57071
This is a roll-forward of https://go.dev/cl/528657, which was reverted
in https://go.dev/cl/543660
Reason for revert: de-flakes tests (reduces dependence on fine-grained
timers, correctly identifies contention on big-endian futex locks,
attempts to measure contention in the semaphore implementation but only
uses that secondary measurement to finish the test early, skips tests on
single-processor systems)
Change-Id: I31389f24283d85e46ad9ba8d4f514cb9add8dfb0
Reviewed-on: https://go-review.googlesource.com/c/go/+/544195
Reviewed-by: Michael Pratt <mpratt@google.com>
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Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Rhys Hiltner <rhys@justin.tv>
Run-TryBot: Rhys Hiltner <rhys@justin.tv>
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This reverts commit go.dev/cl/528657.
Reason for revert: broke a lot of builders.
Change-Id: I70c33062020e997c4df67b3eaa2e886cf0da961e
Reviewed-on: https://go-review.googlesource.com/c/go/+/543660
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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Add runtime-internal locks to the mutex contention profile.
Store up to one call stack responsible for lock contention on the M,
until it's safe to contribute its value to the mprof table. Try to use
that limited local storage space for a relatively large source of
contention, and attribute any contention in stacks we're not able to
store to a sentinel _LostContendedLock function.
Avoid ballooning lock contention while manipulating the mprof table by
attributing to that sentinel function any lock contention experienced
while reporting lock contention.
Guard collecting real call stacks with GODEBUG=profileruntimelocks=1,
since the available data has mixed semantics; we can easily capture an
M's own wait time, but we'd prefer for the profile entry of each
critical section to describe how long it made the other Ms wait. It's
too late in the Go 1.22 cycle to make the required changes to
futex-based locks. When not enabled, attribute the time to the sentinel
function instead.
Fixes #57071
Change-Id: I3eee0ccbfc20f333b56f20d8725dfd7f3a526b41
Reviewed-on: https://go-review.googlesource.com/c/go/+/528657
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This change mostly implements the design described in #60773 and
includes a new scalable parser for the new trace format, available in
internal/trace/v2. I'll leave this commit message short because this is
clearly an enormous CL with a lot of detail.
This change does not hook up the new tracer into cmd/trace yet. A
follow-up CL will handle that.
For #60773.
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-linux-amd64-longtest-race
Change-Id: I5d2aca2cc07580ed3c76a9813ac48ec96b157de0
Reviewed-on: https://go-review.googlesource.com/c/go/+/494187
Reviewed-by: Michael Pratt <mpratt@google.com>
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Change-Id: I1f031f0f83a94bebe41d3978a91a903dc5bcda66
Reviewed-on: https://go-review.googlesource.com/c/go/+/489276
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
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Change-Id: I1c478b704d84811caa209006c657dda82d9c4cf9
Reviewed-on: https://go-review.googlesource.com/c/go/+/488435
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
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Re-enable frame pointer unwinding for execution tracing on amd64 by
default, now that CL 489015 and CL 488755 have fixed recently-discovered
crashes. This reverts CL 486382.
These fixes, together with CL 241158 to fix up frame pointers when
copying stacks on arm64, also make frame pointer unwinding for tracing
safe to enable for arm64. This should significantly reduce the CPU and
latency overhead of execution tracing on arm64, as it has for amd64.
Co-Authored-By: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Change-Id: I64a88bd69dfd8cb13956ec46f8b1203dbeaa26a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/490815
Reviewed-by: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
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For #59670.
Change-Id: I0efa743edc08e48dc8d906803ba45e9f641369db
Reviewed-on: https://go-review.googlesource.com/c/go/+/486977
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Austin Clements <austin@google.com>
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Frame pointer unwinding during execution tracing sometimes crashes.
Until this is diagnosed and fixed, it should be turned off by default.
Updates #59692
Change-Id: I0f2ca24b6d48435b0acfd3da8e4f25b9cfa4ec19
Reviewed-on: https://go-review.googlesource.com/c/go/+/486382
Reviewed-by: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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This reverts commit CL 486381.
Submitted out of order and breaks bootstrap.
Change-Id: Ia472111cb966e884a48f8ee3893b3bf4b4f4f875
Reviewed-on: https://go-review.googlesource.com/c/go/+/486915
Reviewed-by: David Chase <drchase@google.com>
TryBot-Bypass: Austin Clements <austin@google.com>
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For #59670.
Change-Id: I4476d6f92663e8a825d063d6e6a7fc9a2ac99d4d
Reviewed-on: https://go-review.googlesource.com/c/go/+/486381
Run-TryBot: Austin Clements <austin@google.com>
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GOTRACEBACK=wer is a new traceback level that acts as "crash" and
also enables WER. The same effect can be achieved using
debug.SetTraceback("wer").
The Go runtime currently crashes using exit(2), which bypasses WER
even if it is enabled. To best way to trigger WER is calling
RaiseFailFastException [1] instead, which internally launches the
WER machinery.
This CL also changes how GOTRACEBACK=crash crashes, so both "wer" and
"crash" crash using RaiseFailFastException, which simplifies the
implementation and resolves a longstanding TODO.
Fixes #57441
Fixes #20498
[1] https://learn.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-raisefailfastexception
Change-Id: I45669d619fbbd2f6413ce5e5f08425ed1d9aeb64
Reviewed-on: https://go-review.googlesource.com/c/go/+/474915
Reviewed-by: Davis Goodin <dagood@microsoft.com>
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Change tracer to use frame pointer unwinding by default on amd64. The
expansion of inline frames is delayed until the stack table is dumped at
the end of the trace. This requires storing the skip argument in the
stack table, which now resides in pcBuf[0]. For stacks that are not
produced by traceStackID (e.g. CPU samples), a logicalStackSentinel
value in pcBuf[0] indicates that no inline expansion is needed.
Add new GODEBUG=tracefpunwindoff=1 option to use the old unwinder if
needed.
Benchmarks show a considerable decrease in CPU overhead when using frame
pointer unwinding for trace events:
GODEBUG=tracefpunwindoff=1 ../bin/go test -run '^$' -bench '.+PingPong' -count 20 -v -trace /dev/null ./runtime | tee tracefpunwindoff1.txt
GODEBUG=tracefpunwindoff=0 ../bin/go test -run '^$' -bench '.+PingPong' -count 20 -v -trace /dev/null ./runtime | tee tracefpunwindoff0.txt
goos: linux
goarch: amd64
pkg: runtime
cpu: Intel(R) Xeon(R) Platinum 8375C CPU @ 2.90GHz
│ tracefpunwindoff1.txt │ tracefpunwindoff0.txt │
│ sec/op │ sec/op vs base │
PingPongHog-32 3782.5n ± 0% 740.7n ± 2% -80.42% (p=0.000 n=20)
For #16638
Change-Id: I2928a2fcd8779a31c45ce0f2fbcc0179641190bb
Reviewed-on: https://go-review.googlesource.com/c/go/+/463835
Reviewed-by: Michael Pratt <mpratt@google.com>
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This GODEBUG flag disables the freezetheworld call during fatal panic.
freezetheworld asks the scheduler to stop running goroutines on all Ms.
This is normally useful, as it ensures we can collect a traceback from
every goroutine. However, it can be frustrating when debugging the
scheduler itself, as it significantly changes the scheduler state from
when the panic started.
Setting this flag has some disadvantages. Most notably, running
goroutines will not traceback in the standard output (though they may be
included in the final SIGQUIT loop). Additionally, we may missing
concurrently created goroutines when looping over allgs (CL 270861 made
this safe, but still racy). The final state of all goroutines will also
be further removed from the time of panic, as they continued to run for
a while.
One unfortunate part of this flag is the final SIGQUIT loop in the
runtime leaves every thread in the signal handler at exit. This is a bit
frustrating in gdb, which doesn't understand how to step beyond
sigtramp. The data is still there, but you must manually walk.
Change-Id: Ie6bd3ac521fcababea668196b60cf225a0be1a00
Reviewed-on: https://go-review.googlesource.com/c/go/+/478975
Reviewed-by: Austin Clements <austin@google.com>
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