Fixes#13491
Change-Id: Ic0525d8ee90f47d0d23c1485919aee13d2400494
Reviewed-on: https://go-review.googlesource.com/c/139537
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit makes syscall on js/wasm use the asynchronous variants
of functions in Node.js' fs module. This enables concurrency
and allows the API of the fs module to be implemented with an
alternative backend that only supports asynchronous operations.
Updates #26051.
Change-Id: Ibe1dcc988469fc11c3b8d8d49de439c12ddaafce
Reviewed-on: https://go-review.googlesource.com/c/137236
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
When an invalid UTF-8 byte sequence is decoded in a range loop over a string
a utf8.RuneError rune is returned. This is not distinguishable from decoding
the valid '\uFFFD' sequence representing utf8.RuneError from a string without
further checks within the range loop.
The previous Map code did not do any extra checks and would thereby not map
invalid UTF-8 byte sequences correctly when those were mapping to utf8.RuneError.
Fix this by adding the extra checks necessary to distinguish the decoding
of invalid utf8 byte sequences from decoding the sequence for utf8.RuneError
when the mapping of a rune is utf8.RuneError.
This fix does not result in a measureable performance regression:
name old time/op new time/op delta
ByteByteMap 1.05µs ± 3% 1.03µs ± 3% ~ (p=0.118 n=10+10)
Map/identity/ASCII 169ns ± 2% 170ns ± 1% ~ (p=0.501 n=9+10)
Map/identity/Greek 298ns ± 1% 303ns ± 4% ~ (p=0.338 n=10+10)
Map/change/ASCII 323ns ± 3% 325ns ± 4% ~ (p=0.679 n=8+10)
Map/change/Greek 628ns ± 5% 635ns ± 1% ~ (p=0.460 n=10+9)
MapNoChanges 120ns ± 4% 119ns ± 1% ~ (p=0.496 n=10+9)
Fixes#26305
Change-Id: I70e99fa244983c5040756fa4549ac1e8cb6022c3
Reviewed-on: https://go-review.googlesource.com/c/131495
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit adds AIX operating system to internal/poll package for ppc64
architecture.
Updates: #25893
Change-Id: I9b1da9255012de58f16547c1b18f8840485da170
Reviewed-on: https://go-review.googlesource.com/c/138717
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit adds AIX operating system to runtime package for ppc64
architecture.
Only new files and minor changes are in this commit. Others
modifications in files like asm_ppc64.s will be in separate commits.
Updates: #25893
Change-Id: I9c5e073f5f3debb43b004ad1167694a5afd31cfd
Reviewed-on: https://go-review.googlesource.com/c/138716
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Currently, the Windows profile loop isn't robust against racing with
unminit. For example,
T1 is running profileloop1, T2 is another thread
T1: thread := atomic.Loaduintptr(&T2.thread)
T2: calls unminit, which does CloseHandle(T2.thread)
T1: attempts to suspends T2
In this case the SuspendThread will fail, but currently we ignore this
failure and forge ahead, which will cause further failures and
probably bad profile data.
Handle this race by defending against SuspendThread failing. If
SuspendThread succeeds, then we know the thread is no longer going
anywhere.
Change-Id: I4726553239b17f05ca07a0cf7df49631e0cb550d
Reviewed-on: https://go-review.googlesource.com/c/129685
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
The debug call injection tests will freeze when run under a debugger
because they depend on catching SIGTRAP, which is usually swallowed by
a debugger.
Change-Id: If6b86ca279b0489182990dd513444ca3062973f1
Reviewed-on: https://go-review.googlesource.com/c/139437
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
And start using it elsewhere in the standard library, removing the
copies in the process.
While at it, rewrite the io.WriteString godoc to be more clear, since it
can now make reference to the defined interface.
Fixes#27946.
Change-Id: Id5ba223c09c19e5fb49815bd3b1bd3254fc786f3
Reviewed-on: https://go-review.googlesource.com/c/139457
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Allocate a long linked list on the stack. This tests both
lots of live stack objects, and lots of intra-stack pointers
to those objects.
Change-Id: I169e067416455737774851633b1e5367e10e1cf2
Reviewed-on: https://go-review.googlesource.com/c/135296
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
When a function triggers a signal (like a segfault which translates to
a nil pointer exception) during execution, a sigpanic handler is just
below it on the stack. The function itself did not stop at a
safepoint, so we have to figure out what safepoint we should use to
scan its stack frame.
Previously we used the site of the most recent defer to get the live
variables at the signal site. That answer is not quite correct, as
explained in #27518. Instead, use the site of a deferreturn call.
It has all the right variables marked as live (no args, all the return
values, except those that escape to the heap, in which case the
corresponding PAUTOHEAP variables will be live instead).
This CL requires stack objects, so that all the local variables
and args referenced by the deferred closures keep the right variables alive.
Fixes#27518
Change-Id: Id45d8a8666759986c203181090b962e2981e48ca
Reviewed-on: https://go-review.googlesource.com/c/134637
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
The previous CL introduced stack objects. This CL removes the old
ambiguously live liveness analysis. After this CL we're relying
on stack objects exclusively.
Update a bunch of liveness tests to reflect the new world.
Fixes#22350
Change-Id: I739b26e015882231011ce6bc1a7f426049e59f31
Reviewed-on: https://go-review.googlesource.com/c/134156
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Rework how the compiler+runtime handles stack-allocated variables
whose address is taken.
Direct references to such variables work as before. References through
pointers, however, use a new mechanism. The new mechanism is more
precise than the old "ambiguously live" mechanism. It computes liveness
at runtime based on the actual references among objects on the stack.
Each function records all of its address-taken objects in a FUNCDATA.
These are called "stack objects". The runtime then uses that
information while scanning a stack to find all of the stack objects on
a stack. It then does a mark phase on the stack objects, using all the
pointers found on the stack (and ancillary structures, like defer
records) as the root set. Only stack objects which are found to be
live during this mark phase will be scanned and thus retain any heap
objects they point to.
A subsequent CL will remove all the "ambiguously live" logic from
the compiler, so that the stack object tracing will be required.
For this CL, the stack tracing is all redundant with the current
ambiguously live logic.
Update #22350
Change-Id: Ide19f1f71a5b6ec8c4d54f8f66f0e9a98344772f
Reviewed-on: https://go-review.googlesource.com/c/134155
Reviewed-by: Austin Clements <austin@google.com>
This CL removes all unused code from bimport.go and bexport.go.
In the interest of keeping this CL strictly delete-only and easier to
review, the task of consolidating the vestigial code elsewhere is left
to future CLs.
Change-Id: Ib757cc27e3fe814cbf534776d026e4d4cddfc6db
Reviewed-on: https://go-review.googlesource.com/c/139338
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
The new indexed package export format appears stable, and no reports
of needing to revert back to binary package export.
This CL disables the binary package export format by mechanically
replacing 'flagiexport' with 'true', and then superficial code
cleanups to keep the resulting code idiomatic. The resulting dead code
is removed in a followup CL.
Change-Id: Ic30d85f78778a31d279a56b9ab14e80836d50135
Reviewed-on: https://go-review.googlesource.com/c/139337
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Unsuccessful calls to LoadLocation previously returned the first
error encountered while traversing the default list of sources, but
ignored errors from sources specified by ZONEINFO. Whether errors
indicating missing zones or sources were ignored in this process
differed between kinds of sources.
With this change, unsuccessful calls to LoadLocation always return
the first error, not counting errors indicating missing zones or
sources.
Change-Id: Ief2c088f1df53d974b837e6565e784c2b9928ef4
Reviewed-on: https://go-review.googlesource.com/c/81595
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The old one was rather confusing - it makes it sound like the user has done something wrong.
Change-Id: Ibc7411f4f1d5f6c66fbcaac64bb05b0743354418
GitHub-Last-Rev: 09290accdd
GitHub-Pull-Request: golang/go#27979
Reviewed-on: https://go-review.googlesource.com/c/139102
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
If an illegal header write is detected, find the first caller outside of
net/http using runtime.CallersFrames and include the call site in the log
message.
Fixes#18761
Change-Id: I92be00ac206c6ebdd60344ad7bf40a7c4c188547
Reviewed-on: https://go-review.googlesource.com/c/130997
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Don't worry, this patch just remove trailing whitespace from
assembly files, and does not touch any logical changes.
Change-Id: Ia724ac0b1abf8bc1e41454bdc79289ef317c165d
Reviewed-on: https://go-review.googlesource.com/c/113595
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
When deadline has already passed,
current context is canceled before return cancel function.
So is unnecessary to call cancel with remove from parent again
in return cancel function.
Change-Id: I37c687c57a29d9f139c7fb648ce7de69093ed623
Reviewed-on: https://go-review.googlesource.com/c/50410
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
In some optimization rules the type of generated OffPtr was
incorrectly set to the type of the pointee, instead of the
pointer. When the OffPtr value is spilled, this may generate
a spill of the wrong type, e.g. a floating point spill of an
integer (pointer) value. On Wasm, this leads to invalid
bytecode.
Fixes#27961.
Change-Id: I5d464847eb900ed90794105c0013a1a7330756cc
Reviewed-on: https://go-review.googlesource.com/c/139257
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Richard Musiol <neelance@gmail.com>
p = path.Dir(p) converges to either "." or "/". The current
implementation of modload.QueryPackage() has a loop that
terminates only on ".", not "/". This leads to the go command
hanging in an infinite loop if the user manages to supply
a file path starting with "/" as package path.
An example of the issue is if the user (incorrectly) attempts
to use an absolute directory path in an import statement within
a module (import "/home/bob/myproj") and then runs go list.
Fixes#27558
Change-Id: Iaa6a4f7b05eba30609373636e50224ae2e7d6158
GitHub-Last-Rev: 3a70d3a427
GitHub-Pull-Request: golang/go#27976
Reviewed-on: https://go-review.googlesource.com/c/139098
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
This commit adds AIX operating system to cmd/dist package for ppc64
architecture.
The stack guard is increased because of syscalls made inside the runtime
which need a larger stack.
Disable cmd/vet/all tests until aix/ppc64 is fully available.
Change-Id: I7e3caf86724249ae564a152d90c1cbd4de288814
Reviewed-on: https://go-review.googlesource.com/c/138715
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This will clarify that the resources are not completely pushed yet when `Push` returns and that it starts a separate goroutine. This might be implementation dependant but as I believe there is currently only one implementation it should be added to the documentation of the interface which most people will look up first.
Change-Id: Id151c5563fd0c4e611eb1d93b4f64bf747ddf6d4
GitHub-Last-Rev: 1f46eb9a08
GitHub-Pull-Request: golang/go#25025
Reviewed-on: https://go-review.googlesource.com/c/108939
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
In the arm assembler, "AMOVW" never falls into optab
case 13, so the check "if p.As == AMOVW" is useless.
Change-Id: Iec241d5b4cffb358a1477f470619dc9a6287884a
Reviewed-on: https://go-review.googlesource.com/c/138575
Run-TryBot: Ben Shi <powerman1st@163.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
WebSockets requires HTTP/1 in practice (no spec or implementations
work over HTTP/2), so if we get an HTTP request that looks like it's
trying to initiate WebSockets, use HTTP/1, like browsers do.
This is part of a series of commits to make WebSockets work over
httputil.ReverseProxy. See #26937.
Updates #26937
Change-Id: I6ad3df9b0a21fddf62fa7d9cacef48e7d5d9585b
Reviewed-on: https://go-review.googlesource.com/c/137437
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
When http2 fails with ErrNoCachedConn the request is retried with body
that has already been read.
Fixes#25009
Change-Id: I51ed5c8cf469dd8b17c73fff6140ab80162bf267
Reviewed-on: https://go-review.googlesource.com/c/131755
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Now that we do no mark work during mark termination, we no longer need
the gchelper mechanism.
Updates #26903.
Updates #17503.
Change-Id: Ie94e5c0f918cfa047e88cae1028fece106955c1b
Reviewed-on: https://go-review.googlesource.com/c/134785
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Before STW and concurrent GC were unified, there could be either one
or two root marking passes per GC cycle. There were several tasks we
had to make sure happened once and only once (whether that was at the
beginning of concurrent mark for concurrent GC or during mark
termination for STW GC). We kept track of this in work.markrootdone.
Now that STW and concurrent GC both use the concurrent marking code
and we've eliminated all work done by the second root marking pass, we
only ever need a single root marking pass. Hence, we can eliminate
work.markrootdone and all of the code that's conditional on it.
Updates #26903.
Change-Id: I654a0f5e21b9322279525560a31e64b8d33b790f
Reviewed-on: https://go-review.googlesource.com/c/134784
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently, all mcaches are flushed during STW mark termination as a
root marking job. This is currently necessary because all spans must
be out of these caches before sweeping begins to avoid races with
allocation and to ensure the spans are in the state expected by
sweeping. We do it as a root marking job because mcache flushing is
somewhat expensive and O(GOMAXPROCS) and this parallelizes the work
across the Ps. However, it's also the last remaining root marking job
performed during mark termination.
This CL moves mcache flushing out of mark termination and performs it
lazily. We keep track of the last sweepgen at which each mcache was
flushed and as each P is woken from STW, it observes that its mcache
is out-of-date and flushes it.
The introduces a complication for spans cached in stale mcaches. These
may now be observed by background or proportional sweeping or when
attempting to add a finalizer, but aren't in a stable state. For
example, they are likely to be on the wrong mcentral list. To fix
this, this CL extends the sweepgen protocol to also capture whether a
span is cached and, if so, whether or not its cache is stale. This
protocol blocks asynchronous sweeping from touching cached spans and
makes it the responsibility of mcache flushing to sweep the flushed
spans.
This eliminates the last mark termination root marking job, which
means we can now eliminate that entire infrastructure.
Updates #26903. This implements lazy mcache flushing.
Change-Id: Iadda7aabe540b2026cffc5195da7be37d5b4125e
Reviewed-on: https://go-review.googlesource.com/c/134783
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Now work.helperDrainBlock is always false, so we can remove it and
code paths that only ran when it was true. That means we no longer use
the gcDrainBlock mode of gcDrain, so we can eliminate that. That means
we no longer use gcWork.get, so we can eliminate that. That means we
no longer use getfull, so we can eliminate that.
Updates #26903. This is a follow-up to unifying STW GC and concurrent GC.
Change-Id: I8dbcf8ce24861df0a6149e0b7c5cd0eadb5c13f6
Reviewed-on: https://go-review.googlesource.com/c/134782
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Now that STW GC marking is unified with concurrent marking, there
should never be mark work remaining in mark termination. Hence, we can
make that check unconditional.
Updates #26903. This is a follow-up to unifying STW GC and concurrent GC.
Change-Id: I43a21df5577635ab379c397a7405ada68d331e03
Reviewed-on: https://go-review.googlesource.com/c/134781
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently, STW GC works very differently from concurrent GC. The
largest differences in that in concurrent GC, all marking work is done
by background mark workers during the mark phase, while in STW GC, all
marking work is done by gchelper during the mark termination phase.
This is a consequence of the evolution of Go's GC from a STW GC by
incrementally moving work from STW mark termination into concurrent
mark. However, at this point, the STW code paths exist only as a
debugging mode. Having separate code paths for this increases the
maintenance burden and complexity of the garbage collector. At the
same time, these code paths aren't tested nearly as well, making it
far more likely that they will bit-rot.
This CL reverses the relationship between STW GC, by re-implementing
STW GC in terms of concurrent GC.
This builds on the new scheduled support for disabling user goroutine
scheduling. During sweep termination, it disables user scheduling, so
when the GC starts the world again for concurrent mark, it's really
only "concurrent" with itself.
There are several code paths that were specific to STW GC that are now
vestigial. We'll remove these in the follow-up CLs.
Updates #26903.
Change-Id: Ia3883d2fcf7ab1d89bdc9c8ee54bf9bffb32c096
Reviewed-on: https://go-review.googlesource.com/c/134780
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
This adds support for disabling the scheduling of user goroutines
while allowing system goroutines like the garbage collector to
continue running. User goroutines pass through the usual state
transitions, but if we attempt to actually schedule one, it will get
put on a deferred scheduling list.
Updates #26903. This is preparation for unifying STW GC and concurrent
GC.
Updates #25578. This same mechanism can form the basis for disabling
all but a single user goroutine for the purposes of debugger function
call injection.
Change-Id: Ib72a808e00c25613fe6982f5528160d3de3dbbc6
Reviewed-on: https://go-review.googlesource.com/c/134779
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently, isSystemGoroutine varies on whether it considers the
finalizer goroutine a user goroutine or a system goroutine. For the
next CL, we're going to want to always consider the finalier goroutine
a user goroutine, so add a flag that indicates that.
Updates #26903. This is preparation for unifying STW GC and concurrent
GC.
Change-Id: Iafc92e519c13d9f8d879332cb5f0d12164104c33
Reviewed-on: https://go-review.googlesource.com/c/134778
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently, setting GODEBUG=gcrescanstacks=1 enables a debugging mode
where the garbage collector re-scans goroutine stacks during mark
termination. This was introduced in Go 1.8 to debug the hybrid write
barrier, but I don't think we ever used it.
Now it's one of the last sources of mark work during mark termination.
This CL removes it.
Updates #26903. This is preparation for unifying STW GC and concurrent
GC.
Updates #17503.
Change-Id: I6ae04d3738aa9c448e6e206e21857a33ecd12acf
Reviewed-on: https://go-review.googlesource.com/c/134777
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently, checkmarks mode uses the full STW GC infrastructure to
perform mark checking. We're about to remove that infrastructure and,
furthermore, since checkmarks is about doing the simplest thing
possible to check concurrent GC, it's valuable for it to be simpler.
Hence, this CL makes checkmarks even simpler by making it non-parallel
and divorcing it from the STW GC infrastructure (including the
gchelper mechanism).
Updates #26903. This is preparation for unifying STW GC and concurrent
GC.
Change-Id: Iad21158123e025e3f97d7986d577315e994bd43e
Reviewed-on: https://go-review.googlesource.com/c/134776
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
This argument is always gcBackgroundMode since only
debug.gcstoptheworld can trigger a STW GC at this point. Remove the
unnecessary argument.
Updates #26903. This is preparation for unifying STW GC and concurrent
GC.
Change-Id: Icb4ba8f10f80c2b69cf51a21e04fa2c761b71c94
Reviewed-on: https://go-review.googlesource.com/c/134775
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently, we disable GC work caching during mark termination. This is
no longer necessary with the new mark completion detection because
1. There's no way for any of the GC mark termination helpers to have
any real work queued and,
2. Mark termination has to explicitly flush every P's buffers anyway
in order to flush Ps that didn't run a GC mark termination helper.
Hence, remove the code that disposes gcWork buffers during mark
termination.
Updates #26903. This is a follow-up to eliminating mark 2.
Change-Id: I81f002ee25d5c10f42afd39767774636519007f9
Reviewed-on: https://go-review.googlesource.com/c/134320
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Now that there is no mark 2 phase, gcBlackenPromptly is no longer
used.
Updates #26903. This is a follow-up to eliminating mark 2.
Change-Id: Ib9c534f21b36b8416fcf3cab667f186167b827f8
Reviewed-on: https://go-review.googlesource.com/c/134319
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
The mark 2 phase was originally introduced as a way to reduce the
chance of entering STW mark termination while there was still marking
work to do. It works by flushing and disabling all local work caches
so that all enqueued work becomes immediately globally visible.
However, mark 2 is not only slow–disabling caches makes marking and
the write barrier both much more expensive–but also imperfect. There
is still a rare but possible race (~once per all.bash) that can cause
GC to enter mark termination while there is still marking work. This
race is detailed at
https://github.com/golang/proposal/blob/master/design/17503-eliminate-rescan.md#appendix-mark-completion-race
The effect of this is that mark termination must still cope with the
possibility that there may be work remaining after a concurrent mark
phase. Dealing with this increases STW pause time and increases the
complexity of mark termination.
Furthermore, a similar but far more likely race can cause early
transition from mark 1 to mark 2. This is unfortunate because it
causes performance instability because of the cost of mark 2.
This CL fixes this by replacing mark 2 with a distributed termination
detection algorithm. This algorithm is correct, so it eliminates the
mark termination race, and doesn't require disabling local caches. It
ensures that there are no grey objects upon entering mark termination.
With this change, we're one step closer to eliminating marking from
mark termination entirely (it's still used by STW GC and checkmarks
mode).
This CL does not eliminate the gcBlackenPromptly global flag, though
it is always set to false now. It will be removed in a cleanup CL.
This led to only minor variations in the go1 benchmarks
(https://perf.golang.org/search?q=upload:20180909.1) and compilebench
benchmarks (https://perf.golang.org/search?q=upload:20180910.2).
This significantly improves performance of the garbage benchmark, with
no impact on STW times:
name old time/op new time/op delta
Garbage/benchmem-MB=64-12 2.21ms ± 1% 2.05ms ± 1% -7.38% (p=0.000 n=18+19)
Garbage/benchmem-MB=1024-12 2.30ms ±16% 2.20ms ± 7% -4.51% (p=0.001 n=20+20)
name old STW-ns/GC new STW-ns/GC delta
Garbage/benchmem-MB=64-12 138k ±44% 141k ±23% ~ (p=0.309 n=19+20)
Garbage/benchmem-MB=1024-12 159k ±25% 178k ±98% ~ (p=0.798 n=16+18)
name old STW-ns/op new STW-ns/op delta
Garbage/benchmem-MB=64-12 4.42k ±44% 4.24k ±23% ~ (p=0.531 n=19+20)
Garbage/benchmem-MB=1024-12 591 ±24% 636 ±111% ~ (p=0.309 n=16+18)
(https://perf.golang.org/search?q=upload:20180910.1)
Updates #26903.
Updates #17503.
Change-Id: Icbd1e12b7a12a76f423c9bf033b13cb363e4cd19
Reviewed-on: https://go-review.googlesource.com/c/134318
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Nothing currently consumes the flag, but we'll use it in the
distributed termination detection algorithm.
Updates #26903. This is preparation for eliminating mark 2.
Change-Id: I5e149a05b1c878fe1009150da21f8bd8ae2b9b6a
Reviewed-on: https://go-review.googlesource.com/c/134317
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
It turns out if you set GODEBUG=gctrace=2, it enables an obscure
debugging mode that, in addition to printing gctrace statistics, also
does a second STW GC following each regular GC. This debugging mode
has long since lost its value (you could maybe use it to analyze
floating garbage, except that we don't print the gctrace line on the
second GC), and it interferes substantially with the operation of the
GC by messing up the statistics used to schedule GCs.
It's also a source of mark termination GC work when we're in
concurrent GC mode, so it's going to interfere with eliminating mark
2. And it's going to get in the way of unifying STW and concurrent GC.
This CL removes this debugging mode.
Updates #26903. This is preparation for eliminating mark 2 and
unifying STW GC and concurrent GC.
Change-Id: Ib5bce05d8c4d5b6559c89a65165d49532165df07
Reviewed-on: https://go-review.googlesource.com/c/134316
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
