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    Subject2.4 very slow memory access on abit kd7raid (kt400); ten times slower than on kg7raid
    Hi,

    I recently upgraded the motherboard in a small server. Everything else
    stayed the same (discussed below).

    Everything slowed down. The easiest way to demontsrate this is by looking at
    these figures:

    raid5: measuring checksumming speed
    - 8regs : 2343.600 MB/sec
    - 32regs : 1944.000 MB/sec
    - pIII_sse : 4163.600 MB/sec
    - pII_mmx : 3584.400 MB/sec
    - p5_mmx : 4600.800 MB/sec
    -raid5: using function: pIII_sse (4163.600 MB/sec)
    + 8regs : 228.400 MB/sec
    + 32regs : 199.200 MB/sec
    + pIII_sse : 352.000 MB/sec
    + pII_mmx : 316.800 MB/sec
    + p5_mmx : 432.800 MB/sec
    +raid5: using function: pIII_sse (352.000 MB/sec)

    Old motherboard above, new below. (Why it chose pIII_sse even when p5_mmx
    was faster is also an interesting question... :)

    What could be causing this? I believe it is a kernel issue because memtest86
    reports realistic memory bandwidths (about 590MB/s).

    I'm now seeing obscene load averages (in excess of 50 not uncommon), and
    'system' usage according to 'top' is almost always over 50 percent (used to
    be around 15-20 with old motherboard).

    Switching back to the old motherboard solves the problem. Load drops back to
    the usual 0.2-2.

    I use a 2.4.20-pre10-ac2 kernel now; I can't easily try a stock kernel
    because they tend to fail during boot in spectacular ways (perhaps the MB is
    too new?).

    The box has four NICs, moderate network traffic (less than 10Mb/s total, on
    average; I'm routing and firewalling between the subnets). CPU is an AMD
    AthlonXP1800+. I have 1GB of DDR266 RAM.

    I use LVM1 (so I guess I can't easily try a 2.5 kernel until the devmapper
    stuff gets sorted out); I have two ATA133 disks sitting on the HPT372 that's
    integrated on the MB (one disk on each channel). A single EIDE CDROM drive
    is hooked up to the VIA IDE controller.

    Three of the NICs are tulip cards from KTI (Intel 21143PD); the fourth is
    the VIA Rhine integrated on the MB.

    I compiled the kernel optimizing for K7; highmem is enabled; I tried both
    with APIC enabled and disabled (the MB has one). USB support is compiled as
    a module; it doesn't matter whether it's loaded or not. I don't use a
    graphical framebuffer (card is an Ati Rage 128). MTRRs are enabled;
    /proc/mtrr contains this:

    reg00: base=0x00000000 ( 0MB), size=1024MB: write-back, count=1
    reg01: base=0xc0000000 (3072MB), size= 256MB: write-combining, count=1
    reg05: base=0xc0000000 (3072MB), size= 256MB: write-combining, count=1

    I'm running Debian unstable, a Domino server (yuck), tomcat 3 and apache
    1.3.

    A google search for 'kt400 linux slow' and similar phrases turned up nothing
    that looked useful.

    A diff between the bootup messages of the old and the new mb looks like this
    (I omit stuff that doesn't seem relevant):

    - BIOS-e820: 0000000000000000 - 00000000000a0000 (usable)
    + BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
    + BIOS-e820: 000000000009f000 - 00000000000a0000 (reserved)
    BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
    BIOS-e820: 0000000000100000 - 000000003fff0000 (usable)
    BIOS-e820: 000000003fff0000 - 000000003fff3000 (ACPI NVS)
    BIOS-e820: 000000003fff3000 - 0000000040000000 (ACPI data)
    + BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
    + BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
    BIOS-e820: 00000000ffff0000 - 0000000100000000 (reserved)
    ...
    CPU: L2 Cache: 256K (64 bytes/line)
    Intel machine check architecture supported.
    Intel machine check reporting enabled on CPU#0.
    -CPU: After generic, caps: 0383f9ff c1cbf9ff 00000000 00000000
    -CPU: Common caps: 0383f9ff c1cbf9ff 00000000 00000000
    +CPU: After generic, caps: 0383fbff c1cbfbff 00000000 00000000
    +CPU: Common caps: 0383fbff c1cbfbff 00000000 00000000
    CPU: AMD Athlon(tm) XP 1800+ stepping 02
    Enabling fast FPU save and restore... done.
    Enabling unmasked SIMD FPU exception support... done.
    ...
    PCI: Using configuration type 1
    ...
    Bus scan for 01 returning with max=01
    Scanning behind PCI bridge 00:01.0, config 010100, pass 1
    Bus scan for 00 returning with max=01
    -PCI: Bus 01 already known
    -PCI: Using IRQ router VIA [1106/0686] at 00:07.0
    +PCI: Using IRQ router VIA [1106/3177] at 00:11.0
    ...
    ACPI: Core Subsystem version [20011018]
    ACPI: Subsystem enabled
    ACPI: System firmware supports S0 S1 S4 S5
    -Processor[0]: C0 C1, 2 throttling states
    +Processor[0]: C0 C1 C2, 2 throttling states
    ACPI: Power Button (FF) found
    ACPI: Multiple power buttons detected, ignoring fixed-feature
    ACPI: Power Button (CM) found
    ACPI: Sleep Button (CM) found
    +ACPI: Thermal Zone found
    ...
    -VP_IDE: IDE controller at PCI slot 00:07.1
    +VP_IDE: IDE controller at PCI slot 00:11.1
    +PCI: No IRQ known for interrupt pin A of device 00:11.1. Please try using pci=biosirq.
    (NB: I did that and it didn't help.)
    VP_IDE: chipset revision 6
    VP_IDE: not 100% native mode: will probe irqs later
    ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
    -VP_IDE: VIA vt82c686b (rev 40) IDE UDMA100 controller on pci00:07.1
    - ide0: BM-DMA at 0xb400-0xb407, BIOS settings: hda:DMA, hdb:pio
    - ide1: BM-DMA at 0xb408-0xb40f, BIOS settings: hdc:pio, hdd:pio
    -HPT370A: IDE controller at PCI slot 00:13.0
    -PCI: Found IRQ 11 for device 00:13.0
    -HPT370A: chipset revision 4
    -HPT370A: not 100% native mode: will probe irqs later
    +VP_IDE: VIA vt8235 (rev 00) IDE UDMA133 controller on pci00:11.1
    + ide0: BM-DMA at 0xc800-0xc807, BIOS settings: hda:DMA, hdb:pio
    + ide1: BM-DMA at 0xc808-0xc80f, BIOS settings: hdc:pio, hdd:pio
    +HPT372: IDE controller at PCI slot 00:13.0
    +PCI: Found IRQ 10 for device 00:13.0
    +PCI: Sharing IRQ 10 with 00:10.2
    +HPT372: chipset revision 5
    +HPT372: not 100% native mode: will probe irqs later
    HPT37X: using 33MHz PCI clock
    ...

    What can I do to fix or narrow down the problem with the new motherboard?

    Is there any patch that might help?

    I tried playing with the BIOS settings for memory access, but that didn't
    buy me anything either.

    Thanks in advance for any suggestions.

    Andrew

    Ps. I'm not subscribed; I'll check the archives, but I'd be obliged if you
    could Cc: me with replies anyway.

    --
    Andrew Korn (Korn Andras) <korn at chardonnay.math.bme.hu>
    Finger korn at chardonnay.math.bme.hu for pgp key. QOTD:
    "Make love not war." - "I'm married and do both."
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