man/ruby.1: document stack size env variables

[Feature #10197]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47713 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 28 insertions, 0 deletions

diff --git a/man/ruby.1 b/man/ruby.1
index 1c0a7dabc7..8f0c0d1ae7 100644
--- a/man/ruby.1
+++ b/man/ruby.1
@@ -482,6 +482,34 @@ as below.
 % gem help
 .Ed
 .Pp
+.Sh STACK SIZE ENVIRONMENT
+Stack size environment variables are implementation-dependent and
+subject to change with different versions of Ruby.  The VM stack is used
+for pure-Ruby code and managed by the virtual machine.  Machine stack is
+used by the operating system and its usage is dependent on C extensions
+as well as C compiler options.  Using lower values for these may allow
+applications to keep more Fibers or Threads running; but increases the
+chance of SystemStackError exceptions and segmentation faults (SIGSEGV).
+These environment variables are available since Ruby 2.0.0.
+All values are specified in bytes.
+.Pp
+.Bl -hang -compact -width "RUBY_THREAD_MACHINE_STACK_SIZE"
+.It Ev RUBY_THREAD_VM_STACK_SIZE
+VM stack size used at thread creation.
+default: 131072 (32-bit CPU) or 262144 (64-bit)
+.Pp
+.It Ev RUBY_THREAD_MACHINE_STACK_SIZE
+Machine stack size used at thread creation.
+default: 524288 or 1048575
+.Pp
+.It Ev RUBY_FIBER_VM_STACK_SIZE
+VM stack size used at fiber creation.
+default: 65536 or 131072
+.Pp
+.It Ev RUBY_FIBER_MACHINE_STACK_SIZE
+Machine stack size used at fiber creation.
+default: 262144 or 524288
+.Pp
 .Sh SEE ALSO
 .Bl -hang -compact -width "http://www.ruby-lang.org/123"
 .It https://www.ruby-lang.org/