code review 108640043: runtime: remove dedicated scavenger thread

runtime: remove dedicated scavenger thread
A whole thread is too much for background scavenger that sleeps all the time anyway.
We already have sysmon thread that can do this work.
Also remove g->isbackground and simplify enter/exitsyscall.

[dvyukov, 2014-07-14 14:28:19]

Hello golang-codereviews@googlegroups.com (cc: khr@golang.org, rlh@golang.org,
rsc@golang.org),

I'd like you to review this change to
https://dvyukov%40google.com@code.google.com/p/go/

[rsc, 2014-08-25 02:09:46]

LGTM

[dvyukov, 2014-08-25 17:00:01]

*** Submitted as https://code.google.com/p/go/source/detail?r=c157d3790300 ***

runtime: remove dedicated scavenger thread
A whole thread is too much for background scavenger that sleeps all the time
anyway.
We already have sysmon thread that can do this work.
Also remove g->isbackground and simplify enter/exitsyscall.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews, khr, rlh
https://codereview.appspot.com/108640043

[gobot, 2014-08-25 17:10:04]

This CL appears to have broken the freebsd-amd64 builder.
See http://build.golang.org/log/c454fb92400fc16aac449934506e1210f68a0a41