How much CPU should an IDE 44x CD-ROM use?

[Scott Garman]

Hi all,

I recently bought a Yamaha CRW-F1 44x/24x/44x IDE CD-RW drive for my
home machine, to replace an HP 8x/4x/32x SCSI drive I had. I was all
excited until I installed it and found out that reading and writing CDs
really bogs down my system, using 90%+ of my CPU and making it very
choppy. I know that IDE devices use more CPU than SCSI (which, as I
understand it, bypasses the CPU entirely), but this seems a bit much. 

I have an AMD Athlon 1.4 GHz system with 512 MB of DDR RAM, and am
running RedHat 7.3 with the latest kernel. I have two hard drives on the
first IDE channel, and the CD drive is the only one (master) on the
second channel. After extensive searching on Google Groups, I learned
that with the latest kernel you have to enable DMA on CD devices by
adding

options ide-cd dma=1

to your module.conf file, which I did, and also comment out the section
in /etc/rc.sysinit which turns off DMA on CD devices (I noticed that
they have this in RH 7.3, but left it out of the file in 8.0). hdparm
confirms that the drive is using DMA:


~% hdparm /dev/hdc

/dev/hdc:
 HDIO_GET_MULTCOUNT failed: Input/output error
 I/O support  =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 HDIO_GET_NOWERR failed: Input/output error
 readonly     =  0 (off)
 BLKRAGET failed: Input/output error
 HDIO_GETGEO failed: Invalid argument
 HDIO_GET_BUSSTATE failed: Permission denied

and the drive is in EIDE mode:

~% cat /proc/ide/via 
----------VIA BusMastering IDE Configuration----------------
Driver Version:                     3.35
South Bridge:                       VIA vt8233a
Revision:                           ISA 0x0 IDE 0x6
Highest DMA rate:                   UDMA133
BM-DMA base:                        0xfc00
PCI clock:                          33.3MHz
Master Read  Cycle IRDY:            0ws
Master Write Cycle IRDY:            0ws
BM IDE Status Register Read Retry:  yes
Max DRDY Pulse Width:               No limit
-----------------------Primary IDE-------Secondary IDE------
Read DMA FIFO flush:          yes                 yes
End Sector FIFO flush:         no                  no
Prefetch Buffer:              yes                 yes
Post Write Buffer:            yes                 yes
Enabled:                      yes                 yes
Simplex only:                  no                  no
Cable Type:                   80w                 80w
-------------------drive0----drive1----drive2----drive3-----
Transfer Mode:       UDMA      UDMA      UDMA       PIO
Address Setup:       30ns      30ns      30ns     120ns
Cmd Active:          90ns      90ns      90ns      90ns
Cmd Recovery:        30ns      30ns      30ns      30ns
Data Active:         90ns      90ns      90ns     330ns
Data Recovery:       30ns      30ns      30ns     270ns
Cycle Time:          22ns      22ns      60ns     600ns
Transfer Rate:   88.8MB/s  88.8MB/s  33.3MB/s   3.3MB/s

But still, I have the same excessive CPU utilization. I have also tried
disabling the ide-scsi emulation on the drive and just using it as a
CD-ROM drive, to try to isolate this issue, but have seen no
improvement. 

The interesting thing is that the CPU utilization is almost all system
time, not user time. Is this something I can fix, or do these drives
really use up this kind of CPU time? 

TIA,

Scott

PS - nice'ing the ripping process helps very little - I still get some
jerky moments when trying to do web browsing, etc while ripping.

-- 
Scott A. Garman                        Unix System Administrator
sgarman at einstein.unh.edu               UNH Nuclear Physics Group