FreeBSD 7.0-RELEASE available [LWN.net]

FreeBSD 7.0-RELEASE available

Posted Feb 28, 2008 17:29 UTC (Thu) by kripkenstein (subscriber, #43281)
In reply to: FreeBSD 7.0-RELEASE available by rsidd
Parent article: FreeBSD 7.0-RELEASE available

Thanks for the link. For those that want a quick peek, the relevant slides are 18-19.

So, this 15% benchmark is on MySQL. As a single benchmark, it is not that conclusive, but
still very interesting (there was also a benchmark of PostgreSQL, but the 15% figure is from
the MySQL one). Also interesting is that Linux with the new scheduler, CFS, does around 20%
*worse* than an older Linux kernel without CFS.

Is CFS that bad? Anecdotally, I am seeing quite poor multitasking performance on Ubuntu Hardy
over here (bug: https://bugs.launchpad.net/ubuntu/+bug/190754 ). I've heard some people blame
CFS for it, but I really have no idea if that's the case. Perhaps someone here knows more?

P.S. Kudos to Kris Kennaway for writing the slides using Latex/Beamer.

(Log in to post comments)

FreeBSD 7.0-RELEASE available

Posted Feb 28, 2008 17:46 UTC (Thu) by kripkenstein (subscriber, #43281) [Link]

Hmm, perhaps they fixed whatever was wrong in 2.6.23, I have no idea. I am on 2.6.24 on Ubuntu
Hardy here, and there are definitely issues with multitasking and responsiveness.

But the problem might be unrelated to the scheduler (even though that seems an obvious first
guess).

FreeBSD 7.0-RELEASE available

Posted Feb 28, 2008 18:43 UTC (Thu) by cyrus (guest, #36858) [Link]

Looking at your launchpad entry, Kim Krecht suggests that this problem only occurs with
PulseAudio. Can you confirm this?

FreeBSD 7.0-RELEASE available

Posted Feb 28, 2008 19:48 UTC (Thu) by kripkenstein (subscriber, #43281) [Link]

While the issue is most obvious with audio (which uses PulseAudio), it also occurs with video.
If I load a complex webpage in Firefox, for example, while watching a movie in Totem then the
video is shown in a 'jerky' manner during the 100% CPU usage in Firefox.

So, the audio is most noticeable - music is out of rhythm, there is static noise, it's very
distracting - but the poor multitasking is also an issue with video.

In both cases I suspect the issue is mostly on low-end computers. My desktop is an Athlon3000,
downclocked to 1GHz (to keep it cool). Things are very noticeable there. At 2Ghz, you might
not notice it and dismiss the issue, which is why I suspect there aren't more reports of this
bug (most people testing Hardy probably have fast computers).

FreeBSD 7.0-RELEASE available

Posted Feb 28, 2008 23:58 UTC (Thu) by man_ls (subscriber, #15091) [Link]

Hmmm, I was going to suggest the low-latency kernel, but it is only available for Feisty Fawn. Pity, I saw much better responsiveness with it. You could try compiling your own kernel with preempt=voluntary (desktop) or even preempt=realtime.

PulseAudio stuttering

Posted Mar 6, 2008 13:18 UTC (Thu) by midg3t (guest, #30998) [Link]

Are you running pulseaudio at elevated priority?

PulseAudio stuttering

Posted Mar 6, 2008 13:23 UTC (Thu) by kripkenstein (subscriber, #43281) [Link]

Hmm, I didn't make any change to the defaults here. Looking in top, it appears it is at PR 20
and Nice 0.

FreeBSD 7.0-RELEASE available

Posted Mar 2, 2008 3:20 UTC (Sun) by dirtyepic (subscriber, #30178) [Link]

Is CFS that bad? Anecdotally, I am seeing quite poor multitasking performance on Ubuntu Hardy over here (bug: https://bugs.launchpad.net/ubuntu/+bug/190754 ). I've heard some people blame CFS for it, but I really have no idea if that's the case. Perhaps someone here knows more?

I've noticed a lot of latency issues on my laptop running Gentoo, which is generally compiling endlessly (i do a lot of gcc snapshot testing against our tree) which began around the time the kernel switched to CFS, though I can't say it's anything but coincidence and wouldn't have the first clue how to go about finding out. Again, anecdotal evidence, which is usually worse than no evidence at all. ;)