Re: [lto] Add timevars and propagate -v and -save-temps

[Ollie Wild <aaw at google dot com>]

On Sat, Nov 29, 2008 at 9:28 AM, Diego Novillo <dnovillo@google.com> wrote:
>
> -# We have to clear these to avoid problems with this make invocations getting
> +# We have to clear these to avoid problems with this make invocation getting
>  # confused with variables set by (for example) "make -j 2 check".
>  unset MAKEFLAGS
>  unset MAKEINFO

. . . and. . .

> +# Use some simple heuristics to determine how much parallelism to use
> +# when invoking make.  Note that this probably only works reliably on
> +# Linux.  Also, the load may spike right after the calculation, so
> +# it's not foolproof.
> +awk=/usr/bin/awk
> +uptime=/usr/bin/uptime
> +getconf=/usr/bin/getconf
> +par=1
> +if [ -x $awk -a -x $uptime -a -x $getconf ] ; then
> +  loadavg=$($uptime | $awk '{ l = $(NF - 2); print int (strtonum (l)); }')
> +  nprocs=$($getconf _NPROCESSORS_ONLN)
> +  if [ $loadavg -lt $nprocs ] ; then
> +    par=$[($nprocs - $loadavg) * 2]
> +  fi
>  fi
> +${MAKE-make} $quiet -f $makefile -j $par all
> +exit $?

When I wrote the ltrans-driver script, it was my explicit intention to
honor the MAKEFLAGS environment variable in order to manage
parallelism with the parent process.  From the make documentation:

The `-j' option is a special case (*note Parallel Execution:
Parallel.).  If you set it to some numeric value `N' and your operating
system supports it (most any UNIX system will; others typically won't),
the parent `make' and all the sub-`make's will communicate to ensure
that there are only `N' jobs running at the same time between them all.
Note that any job that is marked recursive (*note Instead of Executing
the Commands: Instead of Execution.)  doesn't count against the total
jobs (otherwise we could get `N' sub-`make's running and have no slots
left over for any real work!)

This only works if MAKEFLAGS is inherited from the parent make.  It
looks like you broke this mechanism in a previous change and are now
hacking around that fact.  I'm not quite sure what the issue was that
prompted unsetting MAKEFLAGS, but maybe a better solution is to unset
MAKEFLAGS in the test harness.

Ollie