Re: Benchmarking objrmap under memory pressure

Andrea Arcangeli
2004-04-13T21:59:42Z

On Tue, Apr 13, 2004 at 12:51:11AM -0700, Andrew Morton wrote:
> "Martin J. Bligh" <mbligh@aracnet.com> wrote:
> >
> > UP Athlon 2100+ with 512Mb of RAM. Rebooted clean before each test
> > then did "make clean; make vmlinux; make clean". Then I timed a
> > "make -j 256 vmlinux" to get some testing under mem pressure.
> >
> > I was trying to test the overhead of objrmap under memory pressure,
> > but it seems it's actually distinctly negative overhead - rather pleasing
> > really ;-)
> >
> > 2.6.5
> > 225.18user 30.05system 6:33.72elapsed 64%CPU (0avgtext+0avgdata 0maxresident)k
> > 0inputs+0outputs (37590major+2604444minor)pagefaults 0swaps
> >
> > 2.6.5-anon_mm
> > 224.53user 26.00system 5:29.08elapsed 76%CPU (0avgtext+0avgdata 0maxresident)k
> > 0inputs+0outputs (29127major+2577211minor)pagefaults 0swaps
>
> A four second reduction in system time caused a one minute reduction in
> runtime? Pull the other one ;)
>
> Average of five runs, please...

at the very least the 6 seconds difference on a ~6 minutes load between
anonvma and anonmm sounds smaller than the measurement error generated
by disk seeks for a swapping workload, so yes, I'd like to see all 5
runs (not just the average).

As for the difference between 2.6.5 and 2.6.5-anonvma, that might be the
memory saved by the removal of rmap that in turn reduces the swap-I/O
required to complete the load or something like that, so that one may
not be a measurement error but just the benefit of anon-vma or anonmm,
but for a 6 seconds difference during a swap load I'd definitely like to
see the 5 runs.

Thanks!