fb5230af8a
Currently there are two sensitive periods during which a mutator can allocate past the heap goal but mutator assists can't be enabled: 1) at the beginning of GC between when the heap first passes the heap trigger and sweep termination and 2) at the end of GC between mark termination and when the background GC goroutine parks. During these periods there's no back-pressure or safety net, so a rapidly allocating mutator can allocate past the heap goal. This is exacerbated if there are many goroutines because the GC coordinator is scheduled as any other goroutine, so if it gets preempted during one of these periods, it may stay preempted for a long period (10s or 100s of milliseconds). Normally the mutator does scan work to create back-pressure against allocation, but there is no scan work during these periods. Hence, as a fall back, if a mutator would assist but can't yet, simply yield the CPU. This delays the mutator somewhat, but more importantly gives more CPU time to the GC coordinator for it to complete the transition. This is obviously a workaround. Issue #11970 suggests a far better but far more invasive way to fix this. Updates #11911. (This very nearly fixes the issue, but about once every 15 minutes I get a GC cycle where the assists are enabled but don't do enough work.) Change-Id: I9768b79e3778abd3e06d306596c3bd77f65bf3f1 Reviewed-on: https://go-review.googlesource.com/13026 Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Rick Hudson <rlh@golang.org> |
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README.md
The Go Programming Language
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
For documentation about how to install and use Go, visit https://golang.org/ or load doc/install-source.html in your web browser.
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To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html
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Binary Distribution Notes
If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See https://golang.org/doc/install or doc/install.html for more details.