bogus nice

numerodix · l33t Joined: 18 Jul 2002 Posts: 743 Location: nl.eu

Sorry for reposting this, I thought it would be more fitting here on second thoughts.

I'm wondering how the process priority settings work exactly. Whenever I emerge a new package I preceed the command with "nice -n 19", seemingly relegating the process to the lowest possible priority. When I then monitor the process (and child processes) in top, I find the nice is in fact 19 and the priority (as shown in top) about 35, as compared to ~15 for most other processes. In ps, most processes have a priority of about 75 while the emerge I executed about 99.

But that doesn't stop the compilation process from locking up my desktop, freezing the mouse pointer and the like.

Trying the opposite setting, I run "nice -n -19 emerge -k mozilla". In top, the nice is -19, priority is 6. In ps, the priority is 64. And now too I get lockups of the desktop.

Next experiment, I run xmms with nice -20, ps shows priority 60, top shows 0. I emerge mozilla with nice 19, for the build process top shows priority 36, ps shows 99. Theoretically, xmms runs at the highest possible priority, emerge and all its child processes at the lowest possible, right? No reason to get interrupts in xmms? Well I still do.

I might also mention all other programs run at default priority (nice), none as low as 19, none as high as -2 even.
What am I missing??

Kernel is 2.4.20-gentoo-r1 if that has anything to do with it.

At this point I was advised that the kernel is bugged on this very issue and I switched to vanilla-sources-2.4.20.

Well I switched to vanilla-sources-2.4.20 now, same problem. Mouse pointer freezes and xmms has interrupts.

# cat /proc/version
Linux version 2.4.20 (root@localhost) (gcc version 3.2.2) #1 SMP Sun Mar 30 00:46:36 CET 2003

# top

avendesora · Posted: Sun Mar 30, 2003 8:52 am Post subject:

I don't see anything wrong with your setup.
If you want emerge to run with minimum impact on your perfs. you should

numerodix · l33t Joined: 18 Jul 2002 Posts: 743 Location: nl.eu

nice -20 is the highest priority, nice 19 is the lowest.

avendesora · Posted: Sun Mar 30, 2003 12:22 pm Post subject:

I agree. (Although Niceness and priority are not the same thing.
A process's priority will change during its lifetime depending on how much CPU it has been given. Niceness will never chnage unless someone renices the process).

numerodix · l33t Joined: 18 Jul 2002 Posts: 743 Location: nl.eu

That's fine, I was just pointing out the obvious as I've seen a lot of confusion about the nice values around these forums.

I also think that as long as the system works as it should, the concept with nice is nicer than the Windows way where [to my knowledge] process priority is set absolutely by either the OS or the user.

carpaski · Posted: Sun Mar 30, 2003 6:58 pm Post subject:

As mentioned... It's probably IO.

Try something like this for each disk:

hdparm -c1 -d1 -m32 -u1 /dev/hdX

-m32 might need to be set to -m16, depending on your drives.
_________________
Nicholas Jones <carpaski@gentoo.org>
Gentoo Linux Developer

numerodix · l33t Joined: 18 Jul 2002 Posts: 743 Location: nl.eu

Thanks a bunch!!! My standard test of gunzipping the mozilla sources doesn't torpedo my xmms anymore!

I should have figured that out myself however, I did have a hdparm sentence in local.start but it was overwritten in a merge and I forgot to restore it.