To reduce lock contention in this mode, makes persistent allocation state per-P,
which means at most 64 kB overhead x $GOMAXPROCS, which should be
completely tolerable.
Change-Id: I34ca95e77d7e67130e30822e5a4aff6772b1a1c5
Reviewed-on: https://go-review.googlesource.com/7740
Reviewed-by: Rick Hudson <rlh@golang.org>
This is a follow-up to review comments on CL 7696.
I believe that this includes the first regular Go test in the compiler.
No functional changes. Passes toolstash -cmp.
Change-Id: Id45f51aa664c5d52ece2a61cd7d8417159ce3cf0
Reviewed-on: https://go-review.googlesource.com/7820
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The body tag in the pprof template was misplaced.
Change-Id: Icd7948b358f52df1acc7e033ab27a062990ef977
Reviewed-on: https://go-review.googlesource.com/7795
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This CL updates a TODO on a condition excluding a lot of tests on
android, clarifying what needs to be done. Several of the tests should
be turned off, for example anything depending on the Go tool, others
should be enabled. (See #8345, comment 3 for more details.)
Also add iOS, which has the same set of restrictions.
Tested manually on linux/amd64, darwin/amd64, android/arm, darwin/arm.
Updates #8345
Change-Id: I147f0a915426e0e0de9a73f9aea353766156609b
Reviewed-on: https://go-review.googlesource.com/7734
Reviewed-by: Burcu Dogan <jbd@google.com>
CL 7697 caused doasm failures on 386:
runtime/append_test.go:1: doasm: notfound ft=2 tt=20 00112 (runtime/iface_test.go:207) CMPL $0, BX 2 20
I think that this should be fixed in liblink,
but in the meantime, work around the problem
by instead generating CMPL BX, $0.
Change-Id: I9c572f8f15fc159507132cf4ace8d7a328a3eb4a
Reviewed-on: https://go-review.googlesource.com/7810
Reviewed-by: Keith Randall <khr@golang.org>
Some type assertions of the form _, ok := i.(T) allow efficient inlining.
Such type assertions commonly show up in type switches.
For example, with this optimization, using 6g, the length of
encoding/binary's intDataSize function shrinks from 2224 to 1728 bytes (-22%).
benchmark old ns/op new ns/op delta
BenchmarkAssertI2E2Blank 4.67 0.82 -82.44%
BenchmarkAssertE2T2Blank 4.38 0.83 -81.05%
BenchmarkAssertE2E2Blank 3.88 0.83 -78.61%
BenchmarkAssertE2E2 14.2 14.4 +1.41%
BenchmarkAssertE2T2 10.3 10.4 +0.97%
BenchmarkAssertI2E2 13.4 13.3 -0.75%
Change-Id: Ie9798c3e85432bb8e0f2c723afc376e233639df7
Reviewed-on: https://go-review.googlesource.com/7697
Reviewed-by: Keith Randall <khr@golang.org>
This is preliminary cleanup for another change.
No functional changes. Passes toolstash -cmp.
Change-Id: I11d562fbd6cba5c48d9636f3149e210e5f5308ad
Reviewed-on: https://go-review.googlesource.com/7696
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
The distinction between gcWorkProducer and gcWork (producer and
consumer) is not serving us as originally intended, so merge these
into just gcWork.
The original intent was to replace the currentwbuf cache with a
gcWorkProducer. However, with gchelpwork (aka mutator assists),
mutators can both produce and consume work, so it will make more sense
to cache a whole gcWork.
Change-Id: I6e633e96db7cb23a64fbadbfc4607e3ad32bcfb3
Reviewed-on: https://go-review.googlesource.com/7733
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently markroot fetches the wbuf to fill from the per-M wbuf
cache. The wbuf cache is primarily meant for the write barrier because
it produces very little work on each call. There's little point to
using the cache in mark root, since each call to markroot is likely to
produce a large amount of work (so the slight win on getting it from
the cache instead of from the central wbuf lists doesn't matter), and
markroot does not dispose the wbuf back to the cache (so most markroot
calls won't get anything from the wbuf cache anyway).
Instead, just get the wbuf from the central wbuf lists like other work
producers. This will simplify later changes.
Change-Id: I07a18a4335a41e266a6d70aa3a0911a40babce23
Reviewed-on: https://go-review.googlesource.com/7732
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently, the GC's concurrent mark phase runs on the system
stack. There's no need to do this, and running it this way ties up the
entire M and P running the GC by preventing the scheduler from
preempting the GC even during concurrent mark.
Fix this by running concurrent mark on the regular G stack. It's still
non-preemptible because we also set preemptoff around the whole GC
process, but this moves us closer to making it preemptible.
Change-Id: Ia9f1245e299b8c5c513a4b1e3ef13eaa35ac5e73
Reviewed-on: https://go-review.googlesource.com/7730
Reviewed-by: Rick Hudson <rlh@golang.org>
"Sync" is not very informative. What's being synchronized and with
whom? Update this comment to explain what we're really doing: enabling
write barriers.
Change-Id: I4f0cbb8771988c7ba4606d566b77c26c64165f0f
Reviewed-on: https://go-review.googlesource.com/7700
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently we harvestwbufs the moment we enter the mark phase, even
before starting the world again. Since cached wbufs are only filled
when we're in mark or mark termination, they should all be empty at
this point, making the harvest pointless. Remove the harvest.
We should, but do not currently harvest at the end of the mark phase
when we're running out of work to do.
Change-Id: I5f4ba874f14dd915b8dfbc4ee5bb526eecc2c0b4
Reviewed-on: https://go-review.googlesource.com/7669
Reviewed-by: Rick Hudson <rlh@golang.org>
One of my earlier versions of finer-grained select locking
failed on this test. If you just naively lock and check channels
one-by-one, it is possible that you skip over ready channels.
Consider that initially c1 is ready and c2 is not. Select checks c2.
Then another goroutine makes c1 not ready and c2 ready (in that order).
Then select checks c1, concludes that no channels are ready and
executes the default case. But there was no point in time when
no channel is ready and so default case must not be executed.
Change-Id: I3594bf1f36cfb120be65e2474794f0562aebcbbd
Reviewed-on: https://go-review.googlesource.com/7550
Reviewed-by: Russ Cox <rsc@golang.org>
Just so that we notice in the future if another hash function is added
without updating this utility function, make it panic when passed an
unknown handshake hash function. (Which should never happen.)
Change-Id: I60a6fc01669441523d8c44e8fbe7ed435e7f04c8
Reviewed-on: https://go-review.googlesource.com/7646
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Joël Stemmer <stemmertech@gmail.com>
crypto/rand.Reader doesn't ensure that short reads don't happen. This
change contains a couple of fixups where io.ReadFull wasn't being used
with it.
Change-Id: I3855b81f5890f2e703112eeea804aeba07b6a6b8
Reviewed-on: https://go-review.googlesource.com/7645
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>
For example, "GOARCH=sparc go build -compiler=gccgo" should not crash
merely because the architecture character for sparc is not known.
Change-Id: I18912c7f5d90ef8f586592235ec9d6e5053e4bef
Reviewed-on: https://go-review.googlesource.com/7695
Reviewed-by: Russ Cox <rsc@golang.org>
The value in question is really a bit pattern
(a pointer with extra bits thrown in),
so treat it as a uintptr instead, avoiding the
generation of a write barrier when there
might not be a p.
Also add the obligatory //go:nowritebarrier.
Change-Id: I4ea097945dd7093a140f4740bcadca3ce7191971
Reviewed-on: https://go-review.googlesource.com/7667
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
The GC assumes that there will be no asynchronous write barriers when
the world is stopped. This keeps the synchronization between write
barriers and the GC simple. However, currently, there are a few places
in runtime code where this assumption does not hold.
The GC stops the world by collecting all Ps, which stops all user Go
code, but small parts of the runtime can run without a P. For example,
the code that releases a P must still deschedule its G onto a runnable
queue before stopping. Similarly, when a G returns from a long-running
syscall, it must run code to reacquire a P.
Currently, this code can contain write barriers. This can lead to the
GC collecting reachable objects if something like the following
sequence of events happens:
1. GC stops the world by collecting all Ps.
2. G #1 returns from a syscall (for example), tries to install a
pointer to object X, and calls greyobject on X.
3. greyobject on G #1 marks X, but does not yet add it to a write
buffer. At this point, X is effectively black, not grey, even though
it may point to white objects.
4. GC reaches X through some other path and calls greyobject on X, but
greyobject does nothing because X is already marked.
5. GC completes.
6. greyobject on G #1 adds X to a work buffer, but it's too late.
7. Objects that were reachable only through X are incorrectly collected.
To fix this, we check the invariant that no asynchronous write
barriers happen when the world is stopped by checking that write
barriers always have a P, and modify all currently known sources of
these writes to disable the write barrier. In all modified cases this
is safe because the object in question will always be reachable via
some other path.
Some of the trace code was turned off, in particular the
code that traces returning from a syscall. The GC assumes
that as far as the heap is concerned the thread is stopped
when it is in a syscall. Upon returning the trace code
must not do any heap writes for the same reasons discussed
above.
Fixes#10098Fixes#9953Fixes#9951Fixes#9884
May relate to #9610#9771
Change-Id: Ic2e70b7caffa053e56156838eb8d89503e3c0c8a
Reviewed-on: https://go-review.googlesource.com/7504
Reviewed-by: Austin Clements <austin@google.com>
Some versions of libc, in this case Android's bionic, point environ
directly at the envp memory.
https://android.googlesource.com/platform/bionic/+/master/libc/bionic/libc_init_common.cpp#104
The Go runtime does something surprisingly similar, building the
runtime's envs []string using gostringnocopy. Both libc and the Go
runtime reusing memory interacts badly. When syscall.Setenv uses cgo
to call setenv(3), C modifies the underlying memory of a Go string.
This manifests on android/arm. With GOROOT=/data/local/tmp, a
runtime test calls syscall.Setenv("/os"), resulting in
runtime.GOROOT()=="/os\x00a/local/tmp/goroot".
Avoid this by copying environment string memory into Go.
Covered by runtime.TestFixedGOROOT on android/arm.
Change-Id: Id0cf9553969f587addd462f2239dafca1cf371fa
Reviewed-on: https://go-review.googlesource.com/7663
Reviewed-by: Keith Randall <khr@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>
The Go builders (and standard development cycle) for programs on iOS
require running the programs under lldb. Unfortunately lldb intercepts
SIGSEGV and will not give it back.
https://llvm.org/bugs/show_bug.cgi?id=22868
We get around this by never letting lldb see the SIGSEGV. On darwin,
Unix signals are emulated on top of mach exceptions. The debugger
registers a task-level mach exception handler. We register a
thread-level exception handler which acts as a faux signal handler.
The thread-level handler gets precedence over the task-level handler,
so we can turn the exception EXC_BAD_ACCESS into a panic before lldb
can see it.
Fixes#10043
Change-Id: I64d7c310dfa7ecf60eb1e59f094966520d473335
Reviewed-on: https://go-review.googlesource.com/7072
Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
Fix recover4.go to work on 64kb systems.
Change-Id: I211cb048de1268a8bbac77c6f3a1e0b8c8277594
Reviewed-on: https://go-review.googlesource.com/7673
Reviewed-by: Minux Ma <minux@golang.org>
Updates #10180
Temporarily disable this test on ppc64 systems as all our builders use 64k page size.
We need a portable way to get the page size of the host so we can correctly size the mmap hole.
Change-Id: Ibd36ebe2f54cf75a44667e2070c385f0daaca481
Reviewed-on: https://go-review.googlesource.com/7652
Reviewed-by: Andrew Gerrand <adg@golang.org>
When checkmark fails, greyobject dumps both the object that pointed to
the unmarked object and the unmarked object. This code cluttered up
greyobject, was copy-pasted for the two objects, and the copy for
dumping the unmarked object was not entirely correct.
Extract object dumping out to a new function. This declutters
greyobject and fixes the bugs in dumping the unmarked object. The new
function is slightly cleaned up from the original code to have more
natural control flow and shows a marker on the field in the base
object that points to the unmarked object to make it easy to find.
Change-Id: Ib51318a943f50b0b99995f0941d03ee8876b9fcf
Reviewed-on: https://go-review.googlesource.com/7506
Reviewed-by: Rick Hudson <rlh@golang.org>
scanobject no longer returns the new wbuf.
Change-Id: I0da335ae5cd7ef7ea0e0fa965cf0e9f3a650d0e6
Reviewed-on: https://go-review.googlesource.com/7505
Reviewed-by: Rick Hudson <rlh@golang.org>
This directory is processed by mkbuiltin.go and generates builtin.go.
It should be named builtin too, not builtins, both for consistency
and because file and directory names in general are singular unless
forced otherwise.
Commented on CL 6233 too.
Change-Id: Ic5d3671443ae9292b69fda118f61a11c88d823fa
Reviewed-on: https://go-review.googlesource.com/7660
Reviewed-by: Minux Ma <minux@golang.org>
Also replace proginfo call with cheaper calls where only flags are needed.
Change-Id: Ib6e5c12bd8752b87c0d8bcf22fa9e25e04a7941f
Reviewed-on: https://go-review.googlesource.com/7630
Reviewed-by: Rob Pike <r@golang.org>
- avoid copy in range ytab
- add fast path to prefixof
Change-Id: I88aa9d91a0abe80d253f7c3bca950b4613297499
Reviewed-on: https://go-review.googlesource.com/7628
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
These were introduced during C -> Go translation when the loop increment
contained multiple statements.
Change-Id: Ic8abd8dcb3308851a1f7024de00711f0f984e684
Reviewed-on: https://go-review.googlesource.com/7627
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Rob Pike <r@golang.org>
Substituting in multiple passes meant walking the type
multiple times, and worse, if a complex type was substituted
in an early pass, later passes would follow it, possibly recursively,
until hitting the depth 10 limit.
Change-Id: Ie61d6ec08438e297baabe932afe33d08f358e55f
Reviewed-on: https://go-review.googlesource.com/7625
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Rob Pike <r@golang.org>
In addition to possibly being clearer code,
this replaces an O(n) lookup with an O(log n) lookup.
Change-Id: I0a574c536a965a87f7ad6dcdcc30f737bc771cd5
Reviewed-on: https://go-review.googlesource.com/7623
Reviewed-by: Rob Pike <r@golang.org>
