[sclug] Where to start troubleshooting machine speed?

[Darren Davison]

On Mon, Sep 05, 2005 at 11:45:03AM +0100, Alex Butcher wrote:

> They're the same drivers, but are they the same versions? As you're using
> Gentoo, were all your packages compiled in the same order, using the same
> version of the compiler and with the same flags and features enabled (or,
> preferably, exactly the same binaries)?

after installing the laptop and noticing the difference so markedly, I
recompiled all of the following on the desktop using the same flags: (it was
already the same version of the source as I keep all machines very much up to
date):

GCC, glibc, Xorg, i830/i915 (intel drivers) and the kernel.  They're not the
exact same binaries however.

> If the answer to any of those questions is 'no' or 'don't know', you're not
> performing an apples-to-apples comparison. Getting the same binaries on both
> machines should be the first step in any investigations you make; probably
> the most convenient way for you to do this would be to use Knoppix (or some
> other bootable live CD) temporarily, but installing a binary distro (e.g.
> Fedora, CentOS, SuSE) with the same errata packages installed would also be
> acceptable.

The live CD is a good idea, especially as I can't afford to start
re-installing distros I'm not familiar with on machines I need to use every
day unfortunately :)

> Things I would look at:
> 
> - Disc DMA, interrupt unmasking, 32-bit IO (significant for compilation,
> amongst other things, I find)

On the laptop:
hdparm /dev/hda

/dev/hda:
 multcount    = 16 (on)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 65535/16/63, sectors = 60011642880, start = 0

hdparm -tT /dev/hda
/dev/hda:
 Timing cached reads:   2632 MB in  2.00 seconds = 1316.20 MB/sec
 Timing buffered disk reads:   64 MB in  3.15 seconds =  20.33 MB/sec


and the desktop:
hdparm /dev/hda

/dev/hda:
 multcount    = 16 (on)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 65535/16/63, sectors = 61492838400, start = 0

hdparm -tT /dev/hda

/dev/hda:
 Timing cached reads:   1284 MB in  2.00 seconds = 641.14 MB/sec
 Timing buffered disk reads:   84 MB in  3.05 seconds =  27.57 MB/sec

The cached reads is obviously markedly different there..

> - Check physical configuration of desktop machine (e.g. cabling, jumpers)
> especially if a DIY box (though I've had problems with largeish PC vendors
> misconfiguring the machines they've sold)

it was custom built for me, do you mean check the cabling is secure or
actually test there are no faulty cables?  (Probably beyond me other than
ripping them all out and replacing them)

> - X configuration (for X application performance)

virtually identical on both machines in that they both use DRI and permit the
graphics driver to use an additional 16Mb of system RAM.
 
> - Booting the laptop's kernel with mem=768M to make its configuration more
> closely match that of the desktop.

I'll give it a go.

 
> - Comparing CPUs; cache and frontside-bus speed for a start.

differences in the output of cat /proc/cpuinfo are below.

laptop:
model name      : Intel(R) Pentium(R) M processor 1.70GHz
stepping        : 6
cpu MHz         : 1693.182
cache size      : 2048 KB
flags           : fpu vme de pse tsc msr mce cx8 sep mtrr pge mca cmov pat
clflush dts acpi mmx fxsr sse sse2 ss tm pbe est tm2
bogomips        : 3350.52

desktop:
model name      : Intel(R) Pentium(R) 4 CPU 2.40GHz
stepping        : 4
cpu MHz         : 2412.203
cache size      : 512 KB
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
bogomips        : 4767.74


> HTH,
> Alex.

yep, gives me plenty to start looking at without feeling that I'm shooting in
the dark.  Thanks.

-- 

Darren Davison
Public Key: 0xDD356B0D
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