mirror of https://github.com/golang/go.git
3c3be62201
Moves sweep phase out of stoptheworld by adding background sweeper goroutine and lazy on-demand sweeping. It turned out to be somewhat trickier than I expected, because there is no point in time when we know size of live heap nor consistent number of mallocs and frees. So everything related to next_gc, mprof, memstats, etc becomes trickier. At the end of GC next_gc is conservatively set to heap_alloc*GOGC, which is much larger than real value. But after every sweep next_gc is decremented by freed*GOGC. So when everything is swept next_gc becomes what it should be. For mprof I had to introduce 3-generation scheme (allocs, revent_allocs, prev_allocs), because by the end of GC we know number of frees for the *previous* GC. Significant caution is required to not cross yet-unknown real value of next_gc. This is achieved by 2 means: 1. Whenever I allocate a span from MCentral, I sweep a span in that MCentral. 2. Whenever I allocate N pages from MHeap, I sweep until at least N pages are returned to heap. This provides quite strong guarantees that heap does not grow when it should now. http-1 allocated 7036 7033 -0.04% allocs 60 60 +0.00% cputime 51050 46700 -8.52% gc-pause-one 34060569 1777993 -94.78% gc-pause-total 2554 133 -94.79% latency-50 178448 170926 -4.22% latency-95 284350 198294 -30.26% latency-99 345191 220652 -36.08% rss 101564416 101007360 -0.55% sys-gc 6606832 6541296 -0.99% sys-heap 88801280 87752704 -1.18% sys-other 7334208 7405928 +0.98% sys-stack 524288 524288 +0.00% sys-total 103266608 102224216 -1.01% time 50339 46533 -7.56% virtual-mem 292990976 293728256 +0.25% garbage-1 allocated 2983818 2990889 +0.24% allocs 62880 62902 +0.03% cputime 16480000 16190000 -1.76% gc-pause-one 828462467 487875135 -41.11% gc-pause-total 4142312 2439375 -41.11% rss 1151709184 1153712128 +0.17% sys-gc 66068352 66068352 +0.00% sys-heap 1039728640 1039728640 +0.00% sys-other 37776064 40770176 +7.93% sys-stack 8781824 8781824 +0.00% sys-total 1152354880 1155348992 +0.26% time 16496998 16199876 -1.80% virtual-mem 1409564672 1402281984 -0.52% LGTM=rsc R=golang-codereviews, sameer, rsc, iant, jeremyjackins, gobot CC=golang-codereviews, khr https://golang.org/cl/46430043 |
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README
This is the source code repository for the Go programming language.
For documentation about how to install and use Go,
visit http://golang.org/ or load doc/install-source.html
in your web browser.
After installing Go, you can view a nicely formatted
doc/install-source.html by running godoc --http=:6060
and then visiting http://localhost:6060/doc/install/source.
Unless otherwise noted, the Go source files are distributed
under the BSD-style license found in the LICENSE file.
--
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 README). 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.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 doc/install.html for more details.