High CPU utilization even with DMA enabled?

Wed May 7 15:34:30 PDT 2003

Hi,

Here's the output of top while moving a large file from one disk to
another on my otherwise idle desktop machine:

  PID USERNAME    PRI NICE   SIZE    RES STATE  C   TIME   WCPU    CPU COMMAND
   26 root        -68 -187     0K    12K WAIT   0 141:36 79.98% 79.98% irq7: dc0 ohci0
   11 root        -16   20     0K    12K RUN    1  13:45 34.86% 34.86% idle: cpu1
   12 root        -16   20     0K    12K CPU0   0  13:46 30.32% 30.32% idle: cpu0
21069 root        116    0   608K   136K RUN    1   0:58 16.41% 16.41% mv
  647 dnetc       128   20  1032K   656K RUN    0 826:51  9.28%  9.28% dnetc
  656 dnetc       128   20  1016K   556K RUN    0 829:36  8.15%  8.15% dnetc
   14 root        -48 -167     0K    12K WAIT   0   9:27  4.88%  4.88% swi7: tty:sio clock
    3 root         -8    0     0K    12K g_up   0   4:06  2.88%  2.88% g_up
   24 root        -64 -183     0K    12K WAIT   0   0:27  1.22%  1.22% irq15: ata1

This system has the following IDE configuration:

ATA channel 0:
    Master:      no device present
    Slave:  acd0 <DVD-ROM BDV316C/VER .20H> ATA/ATAPI rev 0
ATA channel 1:
    Master:  ad2 <WDC WD2500JB-34EVA0/15.05R15> ATA/ATAPI rev 6
    Slave:       no device present
ATA channel 2:
    Master:  ad4 <Maxtor 6Y200P0/YAR41VW0> ATA/ATAPI rev 7
    Slave:       no device present
ATA channel 3:
    Master:  ad6 <Maxtor 6Y200P0/YAR41VW0> ATA/ATAPI rev 7
    Slave:       no device present

The files I'm moving are several gigabytes large and they're going from
ad6 to ad2. The motherboard is an Asus A7M266D, with onboard ATA100
channels (0,1) and a Promise Tech ATA133 card installed (channels 2,3).

Now, I realize that copying a file from one disk to another requires cpu
cycles even with DMA enabled, but is 80% of cpu usage to be expected?
Also, wouldn't one expect process id 24 (irq15: ata1) to be using CPU
during such transfers?

Regards,

PS: dmesg, pciconf -vl and other information is available, if needed.

> Andre Guibert de Bruet | Enterprise Software Consultant >
> Silicon Landmark, LLC. | http://siliconlandmark.com/    >