Re: 2.6.24-rc1: First impressions

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

On Fri, 26 Oct 2007 17:22:21 +0200
Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Martin Knoblauch <spamtrap@knobisoft.de> wrote:
> 
> > Hi ,
> > 
> >  just to give some feedback on 2.6.24-rc1. For some time I am tracking 
> >  IO/writeback problems that hurt system responsiveness big-time. I 
> >  tested Peters stuff together with Fenguangs additions and it looked 
> >  promising. Therefore I was very happy to see Peters stuff going into 
> >  2.6.24 and waited eagerly for rc1. In short, I am impressed. This 
> >  really looks good. IO throughput is great and I could not reproduce 
> >  the responsiveness problems so far.
> > 
> >  Below are a some numbers of my brute-force I/O tests that I can use 
> >  to bring responsiveness down. My platform is a HP/DL380g4, dual CPUs, 
> >  HT-enabled, 8 GB Memory, SmartaArray6i controller with 4x72GB SCSI 
> >  disks as RAID5 (battery protected writeback cahe enabled) and gigabit 
> >  networking (tg3). User space is 64-bit RHEL4.3
> > 
> >  I am basically doing copies using "dd" with 1MB blocksize. Local 
> >  Filesystem ist ext2 (noatime). IO-Scheduler is dealine, as it tends 
> >  to give best results. NFS3 Server is a Sun/T2000/Solaris10. The tests 
> >  are:
> > 
> > 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.

> 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(-)