The runtime has historically held two dedicated values g (current goroutine)
and m (current thread) in 'extern register' slots (TLS on x86, real registers
backed by TLS on ARM).
This CL removes the extern register m; code now uses g->m.
On ARM, this frees up the register that formerly held m (R9).
This is important for NaCl, because NaCl ARM code cannot use R9 at all.
The Go 1 macrobenchmarks (those with per-op times >= 10 µs) are unaffected:
BenchmarkBinaryTree17 5491374955 5471024381 -0.37%
BenchmarkFannkuch11 4357101311 4275174828 -1.88%
BenchmarkGobDecode 11029957 11364184 +3.03%
BenchmarkGobEncode 6852205 6784822 -0.98%
BenchmarkGzip 650795967 650152275 -0.10%
BenchmarkGunzip 140962363 141041670 +0.06%
BenchmarkHTTPClientServer 71581 73081 +2.10%
BenchmarkJSONEncode 31928079 31913356 -0.05%
BenchmarkJSONDecode 117470065 113689916 -3.22%
BenchmarkMandelbrot200 6008923 5998712 -0.17%
BenchmarkGoParse 6310917 6327487 +0.26%
BenchmarkRegexpMatchMedium_1K 114568 114763 +0.17%
BenchmarkRegexpMatchHard_1K 168977 169244 +0.16%
BenchmarkRevcomp 935294971 914060918 -2.27%
BenchmarkTemplate 145917123 148186096 +1.55%
Minux previous reported larger variations, but these were caused by
run-to-run noise, not repeatable slowdowns.
Actual code changes by Minux.
I only did the docs and the benchmarking.
LGTM=dvyukov, iant, minux
R=minux, josharian, iant, dave, bradfitz, dvyukov
CC=golang-codereviews
https://golang.org/cl/109050043
For now we don't use CLOCK_MONOTONIC_FAST instead because
it's not supported on prior to 9-STABLE.
Update #6007
LGTM=minux.ma
R=golang-codereviews, minux.ma, bradfitz
CC=golang-codereviews
https://golang.org/cl/68690043
The ARM external linking CL left missed changes to sys_freebsd_arm.s and sys_netbsd_arm.s already done to sys_linux_arm.s.
R=rsc
CC=golang-dev
https://golang.org/cl/12842044
This CL is an aggregate of 10271047, 10499043, 9733044. Descriptions of each follow:
10499043
runtime,cmd/ld: Merge TLS symbols and teach 5l about ARM TLS
This CL prepares for external linking support to ARM.
The pseudo-symbols runtime.g and runtime.m are merged into a single
runtime.tlsgm symbol. When external linking, the offset of a thread local
variable is stored at a memory location instead of being embedded into a offset
of a ldr instruction. With a single runtime.tlsgm symbol for both g and m, only
one such offset is needed.
The larger part of this CL moves TLS code from gcc compiled to internally
compiled. The TLS code now uses the modern MRC instruction, and 5l is taught
about TLS fallbacks in case the instruction is not available or appropriate.
10271047
This CL adds support for -linkmode external to 5l.
For 5l itself, use addrel to allow for D_CALL relocations to be handled by the
host linker. Of the cases listed in rsc's comment in issue 4069, only case 5 and
63 needed an update. One of the TODO: addrel cases was since replaced, and the
rest of the cases are either covered by indirection through addpool (cases with
LTO or LFROM flags) or stubs (case 74). The addpool cases are covered because
addpool emits AWORD instructions, which in turn are handled by case 11.
In the runtime, change the argv argument in the rt0* functions slightly to be a
pointer to the argv list, instead of relying on a particular location of argv.
9733044
The -shared flag to 6l outputs a shared library, implemented in Go
and callable from non-Go programs such as C.
The main part of this CL change the thread local storage model.
Go uses the fastest and least general mode, local exec. TLS data in shared
libraries normally requires at least the local dynamic mode, however, this CL
instead opts for using the initial exec mode. Initial exec mode is faster than
local dynamic mode and can be used in linux since the linker has reserved a
limited amount of TLS space for performance sensitive TLS code.
Initial exec mode requires an extra load from the GOT table to determine the
TLS offset. This penalty will not be paid if ld is not in -shared mode, since
TLS accesses will be reduced to local exec.
The elf sections .init_array and .rela.init_array are added to register the Go
runtime entry with cgo at library load time.
The "hidden" attribute is added to Cgo functions called from Go, since Go
does not generate call through the GOT table, and adding non-GOT relocations for
a global function is not supported by gcc. Cgo symbols don't need to be global
and avoiding the GOT table is also faster.
The changes to 8l are only removes code relevant to the old -shared mode where
internal linking was used.
This CL only address the low level linker work. It can be submitted by itself,
but to be useful, the runtime changes in CL 9738047 is also needed.
Design discussion at
https://groups.google.com/forum/?fromgroups#!topic/golang-nuts/zmjXkGrEx6QFixes#5590.
R=rsc
CC=golang-dev
https://golang.org/cl/12871044
Remove NOPROF/DUPOK from everything.
Edits done with a script, except pclinetest.asm which depended
on the DUPOK flag on main().
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/12613044
This provides a way to generate core dumps when people need them.
The settings are:
GOTRACEBACK=0 no traceback on panic, just exit
GOTRACEBACK=1 default - traceback on panic, then exit
GOTRACEBACK=2 traceback including runtime frames on panic, then exit
GOTRACEBACK=crash traceback including runtime frames on panic, then crash
Fixes#3257.
R=golang-dev, devon.odell, r, daniel.morsing, ality
CC=golang-dev
https://golang.org/cl/7666044
Putting the M initialization in multiple places will not scale.
Various code assumes mstart is the start already. Make it so.
R=golang-dev, devon.odell
CC=golang-dev
https://golang.org/cl/7420048
The naming in this package is a disaster.
Make it all consistent.
Remove some 'static' from functions that will
be referred to from other files soon.
This CL is purely renames using global search and replace.
Submitting separately so that real changes will not
be drowned out by these renames in future CLs.
TBR=iant
CC=golang-dev
https://golang.org/cl/7416046
sysarch requires arguments to be passed on the stack, not in registers.
Credit to Shenghou Ma (minux) for the fix.
R=minux.ma, devon.odell
CC=golang-dev
https://golang.org/cl/7037043
When we release memory to the OS, if the OS doesn't want us
to release it (for example, because the program executed
mlockall(MCL_FUTURE)), madvise will fail. Ignore the failure
instead of crashing.
Fixes#3435.
R=ken2
CC=golang-dev
https://golang.org/cl/6998052
madvise was missing so implement it in assembler. This change
needs to be extended to the other BSD variantes (Net and Open)
Without this change the scavenger will attempt to pass memory back
to the operating system when it has become idle, but the memory is
not returned and for long running Go processes the total memory used
can grow until OOM occurs.
I have only been able to test the code on FreeBSD AMD64. The ARM
platforms needs testing.
R=golang-dev, mikioh.mikioh, dave, jgc, minux.ma
CC=golang-dev
https://golang.org/cl/6850081
