From: "Richard Fish" <bigfish@asmallpond.org>
Subject: Re: [gentoo-user] SATA tuning ?
Date: Tue, 15 Aug 2006 21:47:20 -0700

> Moving this back to gentoo-user, as I accidentally replied off list.
>
> Meino, please don't CC me directly on replies.  I'll read them on the list...

  ...sorry...my fault...bu the previous mail was a private one to me...

> On 8/15/06, Meino Christian Cramer < Meino.Cramer@gmx.de> wrote:
> > > >  WHen doing things, which mixes higher CPU-loads with  massive hd
> > > >  utilization, things are going slow (compilation of Blender for
> > > >  example).
> > >
> > > Ok, let's try to test that.  We'll start by saturating your CPU(s).
> > > On one terminal start "bzip2 -9 < /dev/urandom >/dev/null".
> >
> >   This commandline puts a BIG SMILE onto my face ! Yes, this is as
> >   simple as it is genious!!! Great! Really a nice CPU barbeque !
> >
> > > (If you
> > > have multiple processors, start one of these bzip2 commands on one
> > > terminal for each processor you have).
> > >
> > > Then on another, repeat the "hdparm -Tt /dev/sda"
> >
> >   These are the results __without__ the CPU roaster:
> >
> >     solfire:Mail/vim>sudo hdparm -tT /dev/sda
> >     /dev/sda:
> >     Timing cached reads:   2996 MB in  2.00 seconds = 1499.13 MB/sec
> >     Timing buffered disk reads:  174 MB in   3.01 seconds =  57.79 MB/sec
> >
> >   and this are the results __with__ the CPU roaster:
> >
> > solfire:/home/mccramer>sudo hdparm -Tt /dev/sda
> >     solfire:/home/mccramer>sudo hdparm -Tt /dev/sda
> >     /dev/sda:
> >     Timing cached reads:   2160 MB in  2.10 seconds = 1030.12 MB/sec
> >     Timing buffered disk reads:  174 MB in  3.03 seconds =  57.41 MB/sec
> >
> >
> > The chached reads dropped by ~469MByte/s. The buffered reads are
> > nearly the same.
>
> The buffered reads are all we care about.  They are the actual reads
> from the disk to RAM.  The cached reads is just a repeated read of the
> same sector of the disk, so today is really just a test of your memory
> bandwidth.  Since we are loading memory and the CPU pretty heavily for
> this test, and significant drop is to be expected.

  Ok...sounds good -- in the sense of: It seems, that I have no
  hardware problem anywhere in my Linux box...

> So, it is not CPU utilization that is hurting your performance.

  ( :) imaging the above sentence *WITHOUT* the current context :) )

  This is the eigth wonder of the world...the first time when CPU load
  does *not* hurt system performance! Oh yeah! I will send all my
  render tasks to the...floppy controller, hahahahahahaa :))))))

  (sorry could not resist...I am a little daft this morning as it seems :O))

> You mentioned problems compiling.  The most likely case I can think of
> is that you do not have enough memory, and are inducing the system to
> swap.

  Hmmm...1GByte Dualchannel-RAM should be enough for compiling Blender
  (for example).

> Indeed when compiling most programs, you should see very little
> if any disk activity.

  My SATA disk (Seagate ST3200827AS) is heavily shakeing its head when
  compiling...

> This is particularly suspect if you have
> something like MAKEOPTS=-j4.

  Yes, normally I use "make -j 4" for useing both cores.

  May be I foolishly forget something to switch on or off in my BIOS
  while migrating from PATA to SATA ? The only PATAs in my system is a
  Plextor CD reader/burner and a LG DVD reader/burner on IDE1
  (scnd. channel).

  My mobo is a ASUS AV8 with AMI BIOS (upgraded to the "newest"
  version I could find on the net).

> Regards,
> -Richard
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