Parallel builds in 3.1 branch?

[Mark Mitchell]

--On Thursday, May 16, 2002 06:53:16 PM -0700 "David S. Miller" 
<davem@redhat.com> wrote:

>    From: "Billinghurst, David (CRTS)" <David.Billinghurst@riotinto.com>
>    Date: Fri, 17 May 2002 11:31:07 +1000
>
>    Bootstrap time on cygwin for 3.2 with java increased by factor of 2-3
>    about the time this patch went in.  All the increase seems to be in
>    libjava.
>
>    I don't have accurate times, but it used to bootstrap and test
> overnight    on a 1.5 GHz P4, and now it takes around 24 hours.
>
> Mark does your patch result in more file manipulations?
>
> That is usually the killer that only shows up clearly on
> non-Linux systems.

There are two components to the change:

  1. In the Makefile, use a pattern rule to build things, rather than
     a shell loop.

     Assuming that Make itself is not ridiculously inefficient, this
     shouldn't make a difference.

  2. For safety, the compiler now writes out "foo.tmp" and renames it
     to "foo.class", rather than creating "foo.class" directly.  This
     means that per compiler invocation there is one more file system
     operation.

     I'd be surprised if this did anything like double the time, but
     you never know.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com