Laggy performance during cd-rom usage

Vgui · 09-20-2005, 12:14 AM

Recently while copying a large file from a cdrom (/dev/hdc which I mount at /mnt/cdrom) to my local partition (/dev/hda1) I noticed that performance was seriously lagging. Normally I can compile or play games (basically run the CPU at 99-100%) and not notice this same lag. The mouse pointer was jolting all around the screen instead of a smooth motion.
I had heard something about keeping the cd drive and hard drive on seperate IDE channels or something...any ideas?

aus9 · 09-20-2005, 09:31 AM

I am assuming your optical drive connects to an IDE controller like a hard drive and not to a SCSI?

in which case, generally speaking the data transfer is only as fast as the slowest machine.
if you can....... set the optical to master and have it on its own ribbon/controller.

2) you can do your own real world tests without a program and with an intensive program running....maybe you have a hardware starting to the road to heaven?
could be ram so use memtest
could be harddrive could be optical etc.

find a known size large file and burn it to cdr and copy it back to hard drive from optical drive to see what it is versus do a google for the specs for your optical drive. Then repeat with your fav game running.

3) you can get stats from various linux executables like
top
ps
Gkrellm

aus9 · 09-20-2005, 09:35 AM

eg my cd transfer rate is 7800 Kb per sec vs 21600 for dvd

addy86 · 09-20-2005, 12:17 PM

If your drives use DMA, the CPU is hardly affected, no matter how slow the media are.
Try the following (as root):
hdparm /dev/hda
hdparm /dev/hdc
What does each say for using_dma?

Vgui · 09-20-2005, 03:32 PM

Yes, my hard drives and CD drive are connected with IDE, not SCSI. I don't think it is an upcoming hardware failure, as everything runs fine under my Windows partition, and the RAM is fairly new. I'm away from my computer right now, but I'll check if DMA is enabled on my CD drive when I get home (I know that it is on for my hard drive). I think that maybe DMA isn't on the CD drive, which would explain a lot. The CD drive is 52x speed btw.
Thanks for the help.

foo_bar_foo · 09-20-2005, 10:18 PM

you can up the nice value on the copy so the kernel might relax a bit about handeling those cd drive interupts

addy86 · 09-21-2005, 01:29 AM

IMHO the nice value has nothing to do with the kernel, only with the amount of CPU time granted to the process.

Vgui · 09-21-2005, 01:34 AM

Well, it turns out you had it right addy86, as here is the results from hdparm /dev/hdc

Code:

 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  0 (off)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)

I guess I'll have to throw on DMA for the cd drive and give it a go! Thanks for the help and ideas, I'll try out giving copy a nice value, but that seems more like a temporary solution.

addy86 · 09-21-2005, 04:13 AM

Switching on DMA with hdparm -d will only last until the next reboot.

But usually DMA should be enabled for every device that supports it. Do you use a custom kernel? If yes, what does
grep IDEDMA_PCI_AUTO .config
and
grep IDEDMA_ONLYDISK .config
say (the first should be "yes", the second "no")?