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This CL removes the GOEXPERIMENT=nounified knob, and any conditional
statements that depend on that knob. Further CLs to remove unreachable
code follow this one.
Updates #57410.
Change-Id: I39c147e1a83601c73f8316a001705778fee64a91
Reviewed-on: https://go-review.googlesource.com/c/go/+/458615
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
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This change adds a new GODEBUG flag called pagetrace that writes a
low-overhead trace of how pages of memory are managed by the Go runtime.
The page tracer is kept behind a GOEXPERIMENT flag due to a potential
security risk for setuid binaries.
Change-Id: I6f4a2447d02693c25214400846a5d2832ad6e5c0
Reviewed-on: https://go-review.googlesource.com/c/go/+/444157
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
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This change adds the arenas package and a function to reflect for
allocating from an arena via reflection, but all the new API is placed
behind a GOEXPERIMENT.
For #51317.
Change-Id: I026d46294e26ab386d74625108c19a0024fbcedc
Reviewed-on: https://go-review.googlesource.com/c/go/+/423361
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
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Add a new "coverageredesign" GOEXPERIMENT (currently off by default),
for gating the use of the new code coverage design/implementation.
Updates #51430.
Change-Id: Ia61da869fcd0d61c6163f734e2fe5e3705f37a91
Reviewed-on: https://go-review.googlesource.com/c/go/+/395894
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Austin Clements <austin@google.com>
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Not hooked up to everything else yet.
Copy of CL 395880, for setting up GOEXPERIMENT=boringcrypto
builder ahead of merge.
For #51940.
Change-Id: If842761f77d07329d88748990b95f4b39c2f153a
Reviewed-on: https://go-review.googlesource.com/c/go/+/397895
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
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Reviewed-by: Ian Lance Taylor <iant@golang.org>
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Now that Go 1.18 has been released, remove the old pacer.
Change-Id: Ie7a7596d67f3fc25d3f375a08fc75eafac2eb834
Reviewed-on: https://go-review.googlesource.com/c/go/+/393396
Trust: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
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regabireflect goexperiment was helpful in the register ABI
development, to control code paths for reflect calls, before the
compiler can generate register ABI everywhere. It is not necessary
for now. Drop it.
Change-Id: I2731197d2f496e29616c426a01045c9b685946a4
Reviewed-on: https://go-review.googlesource.com/c/go/+/393362
Trust: Cherry Mui <cherryyz@google.com>
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The new minimum heap of 512 KiB has been the cause of some build
slowdown (~1%) and microbenchmark slowdown (usually ~0%, up to ~50%)
because of two reasons:
1. Applications with lots of small short-lived processes execute many
more GC cycles.
2. Applications with heaps <4 MiB GC up to 8x more often.
In many ways these consequences are inevitable given how GOGC works,
however we need to investigate more as to whether the apparent slowdowns
are indeed unavoidable or if the GC has issues scaling down, which it's
too late for for this release.
Given that this release is already huge, it's OK to push this back.
We'll take a closer look at it next cycle, so place block it behind a
new goexperiment to allow users and ourselves to easily experiment with
it.
Fixes #49744.
Updates #44167.
Change-Id: Ibad51f7873de7517490c89802f3c593834e77ff0
Reviewed-on: https://go-review.googlesource.com/c/go/+/368137
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
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Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: David Chase <drchase@google.com>
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This change implements the GC pacer redesign outlined in #44167 and the
accompanying design document, behind a GOEXPERIMENT flag that is on by
default.
In addition to adding the new pacer, this CL also includes code to track
and account for stack and globals scan work in the pacer and in the
assist credit system.
The new pacer also deviates slightly from the document in that it
increases the bound on the minimum trigger ratio from 0.6 (scaled by
GOGC) to 0.7. The logic behind this change is that the new pacer much
more consistently hits the goal (good!) leading to slightly less
frequent GC cycles, but _longer_ ones (in this case, bad!). It turns out
that the cost of having the GC on hurts throughput significantly (per
byte of memory used), though tail latencies can improve by up to 10%! To
be conservative, this change moves the value to 0.7 where there is a
small improvement to both throughput and latency, given the memory use.
Because the new pacer accounts for the two most significant sources of
scan work after heap objects, it is now also safer to reduce the minimum
heap size without leading to very poor amortization. This change thus
decreases the minimum heap size to 512 KiB, which corresponds to the
fact that the runtime has around 200 KiB of scannable globals always
there, up-front, providing a baseline.
Benchmark results: https://perf.golang.org/search?q=upload:20211001.6
tile38's KNearest benchmark shows a memory increase, but throughput (and
latency) per byte of memory used is better.
gopher-lua showed an increase in both CPU time and memory usage, but
subsequent attempts to reproduce this behavior are inconsistent.
Sometimes the overall performance is better, sometimes it's worse. This
suggests that the benchmark is fairly noisy in a way not captured by the
benchmarking framework itself.
biogo-igor is the only benchmark to show a significant performance loss.
This benchmark exhibits a very high GC rate, with relatively little work
to do in each cycle. The idle mark workers are quite active. In the new
pacer, mark phases are longer, mark assists are fewer, and some of that
time in mark assists has shifted to idle workers. Linux perf indicates
that the difference in CPU time can be mostly attributed to write-barrier
slow path related calls, which in turn indicates that the write barrier
being on for longer is the primary culprit. This also explains the memory
increase, as a longer mark phase leads to more memory allocated black,
surviving an extra cycle and contributing to the heap goal.
For #44167.
Change-Id: I8ac7cfef7d593e4a642c9b2be43fb3591a8ec9c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/309869
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
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Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
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requirements
RegabiG and regabiDefer have been always enabled and removed from
experiments. Update the comment.
Change-Id: Ieaf4b4f0a7e0e9d6733a18932ca457be4f150d08
Reviewed-on: https://go-review.googlesource.com/c/go/+/341150
Trust: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
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Setting `-gcflags=all=-d=unified` works for normal builds/tests, but
seems to have trouble with the test/run.go regress tests. So add a
GOEXPERIMENT knob to allow another way to turn on unified IR
construction, which plays better with all.bash.
While here, update two existing test expectations that currently fail
during GOEXPERIMENT=unified ./all.bash:
1. misc/cgo/errors/testdata/err2.go is testing column positions, and
types2 gets one case slightly better, and another case slightly
worse. For now, the test case is updated to accept both.
2. fixedbugs/issue42284.go is added to the list of known failures,
because it fails for unified IR. (It's an escape analysis test, and
escape analysis is working as expected; but unified is formatting an
imported constant value differently than the test's regexp expects.)
Updates #46786.
Change-Id: I40a4a70fa1b85ac87fcc85a43687f5d81e011ec0
Reviewed-on: https://go-review.googlesource.com/c/go/+/328215
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
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Always enable regabig on AMD64, which enables the G register and
the X15 zero register. Remove the fallback path.
Also remove the regabig GOEXPERIMENT. On AMD64 it is always
enabled (this CL). Other architectures already have a G register,
except for 386, where there are too few registers and it is
unlikely that we will reserve one. (If we really do, we can just
add a new experiment).
Change-Id: I229cac0060f48fe58c9fdaabd38d6fa16b8a0855
Reviewed-on: https://go-review.googlesource.com/c/go/+/327272
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
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Hardwire regabidefers to true. Remove it from GOEXPERIMENTs.
Fallback paths are not cleaned up in this CL. That will be done
in later CLs.
Change-Id: Iec1112a1e55d5f6ef70232a5ff6e702f649071c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/325913
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
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Rerun the generator. exp_regabi_{on,off}.go are gone, as "regabi"
itself is not a goexperiment that we test at run time (the
sub-experiments are).
Change-Id: Ic1f31b4ef2769a143f768e1b3dc7221041aafca9
Reviewed-on: https://go-review.googlesource.com/c/go/+/325912
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
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Currently, specifying GOEXPERIMENT=regabi will turn on all regabi
sub-experiments, but GOEXPERIMENT=noregabi won't turn anything off.
Regabi also isn't a "real" experiment in the sense that nothing in the
code base should depend on it as an experiment flag (it should depend
on the appropriate sub-experiments).
Hence, drop Regabi from goexperiment.Flags and make "regabi" in
GOEXPERIMENT be a real alias for all of the sub-flags, so regabi will
turn on all of the sub-flags and noregabi will turn off all of the
sub-flags.
This way, once we enable the sub-experiments in the baseline
configuration, it will be easy to turn off with "noregabi".
For #40724.
Change-Id: I0fb95be42f756d412e729a396be607d629ae2bab
Reviewed-on: https://go-review.googlesource.com/c/go/+/310609
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
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The go/build package needs access to this configuration,
so move it into a new package available to the standard library.
Change-Id: I868a94148b52350c76116451f4ad9191246adcff
Reviewed-on: https://go-review.googlesource.com/c/go/+/310731
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
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We need to adjust baseline experiment configuration based on the
configured GOOS and GOARCH, so it can't live in goexperiment. Move it
to objabi.
Change-Id: I65f4ce56902c6c1a82735050773c58f2d1320cc6
Reviewed-on: https://go-review.googlesource.com/c/go/+/310169
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
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This adds the set of GOEXPERIMENTs to the build version if it differs
from the default set of experiments. This exposes the experiment
settings via runtime.Version() and "go version <binary>".
Change-Id: I143dbbc50f66a4cf175469199974e18848075af6
Reviewed-on: https://go-review.googlesource.com/c/go/+/307820
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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Right now the rules around handling default-on experiments are
complicated and a bit inconsistent. Notably, objabi.GOEXPERIMENT is
set to a comma-separated list of enabled experiments, but this may not
be the string a user should set the GOEXPERIMENT environment variable
to get that list of experiments: if an experiment is enabled by
default but gets turned off by GOEXPERIMENT, then the string we report
needs to include "no"+experiment to capture that default override.
This complication also seeps into the version string we print for "go
tool compile -V", etc. This logic is further complicated by the fact
that it only wants to include an experiment string if the set of
experiments varies from the default.
This CL rethinks how we handle default-on experiments. Now that
experiment state is all captured in a struct, we can simplify a lot of
this logic. objabi.GOEXPERIMENT will be set based on the delta from
the default set of experiments, which reflects what a user would
actually need to pass on the command line. Likewise, we include this
delta in the "-V" output, which simplifies this logic because if
there's nothing to show in the version string, the delta will be
empty.
Change-Id: I7ed307329541fc2c9f90edd463fbaf8e0cc9e8ee
Reviewed-on: https://go-review.googlesource.com/c/go/+/307819
Trust: Austin Clements <austin@google.com>
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Currently, we have boolean and integral constants for GOEXPERIMENTs in
various places. Consolidate these into automatically generated
constants in the internal/goexperiment package.
Change-Id: I42a49aba2a3b4c722fedea23a613162cd8a67bee
Reviewed-on: https://go-review.googlesource.com/c/go/+/307818
Trust: Austin Clements <austin@google.com>
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Currently there's knowledge about the list of GOEXPERIMENTs in a few
different places. This CL introduces a new package and consolidates
the list into one place: the internal/goexperiment.Flags struct type.
This package gives us a central place to document the experiments as
well as the GOEXPERIMENT environment variable itself. It will also
give us a place to put built-time constants derived from the enabled
experiments.
Now the objabi package constructs experiment names by reflecting over
this struct type rather than having a separate list of these names
(this is similar to how the compiler handles command-line flags and
debug options). We also expose a better-typed API to the toolchain for
propagating enabled experiments.
Change-Id: I06e026712b59fe2bd7cd11a869aedb48ffe5a4b7
Reviewed-on: https://go-review.googlesource.com/c/go/+/307817
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
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