Re: 2.6.24-rc1: First impressions

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 26 Oct 2007 21:33:40 +0200
Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > > > dd1 - copy 16 GB from /dev/zero to local FS
> > > > dd1-dir - same, but using O_DIRECT for output
> > > > dd2/dd2-dir - copy 2x7.6 GB in parallel from /dev/zero to local FS
> > > > dd3/dd3-dir - copy 3x5.2 GB in parallel from /dev/zero lo local FS
> > > > net1 - copy 5.2 GB from NFS3 share to local FS
> > > > mix3 - copy 3x5.2 GB from /dev/zero to local disk and two NFS3 shares
> > > > 
> > > >  I did the numbers for 2.6.19.2, 2.6.22.6 and 2.6.24-rc1. All units 
> > > >  are MB/sec.
> > > > 
> > > > test           2.6.19.2     2.6.22.6    2.6.24.-rc1
> > > > ----------------------------------------------------------------
> > > > dd1                  28           50             96
> > > > dd1-dir              88           88             86
> > > > dd2              2x16.5         2x11         2x44.5
> > > > dd2-dir            2x44         2x44           2x43
> > > > dd3               3x9.8        3x8.7           3x30
> > > > dd3-dir          3x29.5       3x29.5         3x28.5
> > > > net1              30-33        50-55          37-52
> > > > mix3              17/32        25/50          96/35 (disk/combined-network)
> > > 
> > > wow, really nice results!
> > 
> > Those changes seem suspiciously large to me.  I wonder if there's less 
> > physical IO happening during the timed run, and correspondingly more 
> > afterwards.
> 
> so a final 'sync' should be added to the test too, and the time it takes 
> factored into the bandwidth numbers?

That's one way of doing it.  Or just run the test for a "long" time.  ie:
much longer than (total-memory / disk-bandwidth).  Probably the latter
will give a more accurate result, but it can get boring.

> > > I think the MM should get out of deep-feature-freeze mode - there's 
> > > tons of room to improve :-/
> >
> > Kidding.  We merge about 265 MM patches in 2.6.24-rc1:
> >
> >  482 files changed, 8071 insertions(+), 5142 deletions(-)
> 
> impressive :)

A lot of that was new functionality.  That's easier to add than things
which change long-standing functionality.