Re: GNU make 3.99.92 release candidate is available

[Paul Smith]

On Wed, 2013-09-25 at 13:51 +0200, Boris Kolpackov wrote:
> Paul D. Smith <address@hidden> writes:
> > I'm not sure I fully understood the situation.
> > 
> > This comment makes it sound like same version of make (same code) is 50%
> > slower on the new system.  Is that what you meant?
> 
> Yes, the same make binary is 50% faster on 2-generations old Xeon
> compared to the current one. On the old system 3.99 is quite a
> bit faster than 3.82 (don't remember the actual numbers, i think
> it was about 30-40%). On the new box this difference is completely
> wiped-out; both versions take about the same amount of time.

Nice!  Are they running the same distro?  Same kernel and libc versions
anyway (that's about all make uses)?

If you run "make -d" do you get essentially the same output for both?
Maybe something in the environment or something in one of them is
causing make to do a lot more work.

> > The only really variable thing in a do-nothing make build is the
> > amount of time it takes to stat all the files.
> 
> Well, make also has to do a lot of memory-intensive processing (entering
> files into caches, creating all the dependency structures, pattern
> matching, etc). It could be some bad CPU cache interaction. That was
> my first thought since everything on this machine is faster, CPU,
> disks, memory.

Maybe... you'd need to use perf to find out stuff like that I expect.