On Fri, 26 Oct 2007 12:21:55 -0700
Andrew Morton <[email protected]> wrote:
> On Fri, 26 Oct 2007 17:22:21 +0200
> Ingo Molnar <[email protected]> wrote:
>
> >
> > * Martin Knoblauch <[email protected]> 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.
>
another option... this is ext2.. didn't the ext2 reservation stuff get
merged into -rc1? for ext3 that gave a 4x or so speed boost (much
better sequential allocation pattern)
(or maybe I'm just wrong)
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