Red Hat Bugzilla – Bug 64525
Lack of dma on cdrom drives causes extremely poor interactive performance
Last modified: 2014-03-16 22:27:24 EDT
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.0+) Gecko/20020501
Description of problem:
I fresh installed Redhat 7.3 today. I found while burning extra copies of Redhat
7.3 that with the new default of disabling dma on my cdrom drives caused
extremely poor interactive performance. I have seen it seem to freeze and then
job from 82% to 100% burning, and the mouse wouldn't move. By using hdparm -d1
/dev/hdc to reenable dma I was able to fix the problem. The comments in
rc.sysinit suggest that dma on is problematic for some, but it is also
problematic for others off. I also have read another bug report about skipjack
beta that someone couldn't use their cd burner drive at all with dma disabled. I
think the lines to disable dma on cdrom drives should be removed or at least
commented out in a future release.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. login as a user
2. run xcdroast
3. select iso to burn
4. start burning iso
Actual Results: The screen redraws slowly or freezes for seconds at a time.
Expected Results: Interactively of X to be normal
I am noticed this while burning at 24X. I suspect that 4x wouldn't be that
noticable, but 24X definitely is for me. I have a ABIT KT7A-RAID and the CDRW
drive is on the secondary VIA IDE controller. I am using the default, out of the
box/compiled by redhat, kernel for Redhat 7.3.
This was done intentionally, as many CD-ROM drives do not have proper DMA support.
You can create /etc/sysconfig/harddisk<device> that has:
to reenable it on boot.