Phoronix has run some tests comparing the openSUSE 11.1 release candidate (RC1), Ubuntu 8.10, Fedora 10 and Mandriva 2009.0 on Intel Atom.
We have looked at the results and they are not good for openSUSE 11.1. I’ve talked with a few engineers and want to present below our first analysis.
While the benchmarks were done on a specific hardware, they might be relevant for other hardware as well.
Note that the numbers I cite below are not benchmark numbers comparable to the one Phoronix measured, they are measured on totally different machines by different engineers and not all are done as real benchmarks. But they show some of the problems.
Disk I/O – Safe or Fast?
We have barriers enabled for the ext3 filesystem. This is needed for filesystem integrity but forces at certain points a flush of disk writeback caches to prevent data corruption.
As Wikipedia states:
“Ext3 does not do checksumming when writing to the journal. If barrier=1 is not enabled as a mount option (in /etc/fstab), and if the hardware is doing out-of-order write caching, one runs the risk of severe filesystem corruption during a crash.”
With openSUSE barrier=1 is the default and even AFAIK openSUSE and SUSE Linux Enterprise are the only distributions enabling barriers by default.
If you want to disable barriers, use “mount -o barrier=0″ on ext3 (or change /etc/fstab).
The gzip test for example gives on one of our machines the following results:
kernel-default-188.8.131.52-1.1 / ext3: 1348s
kernel-default-184.108.40.206-1.1 / ext3 barrier=0: 437s
X11 and Graphics – Performance of the Intel Driver
Looking at the graphics results, I see that OpenGL has the same performance but XRender is horribly slow, but Ubuntu sometimes(!) hits the same issue.
We have an upstream bug open about X11 speed (see here), and it’s considered the highest priority bug, still nobody has a clue where it comes from. This needs to be rechecked with the final version of openSUSE 11.1, though, because there are some indications that it got improved. Intel has apparently fixed some of that in a newer driver that is not available yet.
It would also be interesting to know whether Mandriva uses XAA or EXA, we do not use XAA for Intel driver any longer, since Intel as driver author does not want to support it, and it has issues with suspend and resume. The old XAA is currently better optimized than the new EXA.
Performance is Important
Performance is important for us and our engineers are working on performance improvements and try to help with known regressions.
For example, if you look at discussions about the tbench regression (LWN reports about these at “Tracking tbench troubles” and “Tbench troubles II“, you see a couple of Novell engineers involved including Rafael Wysocki and Jiri Kosina – and we have run quite some benchmarks to help track and fix these problems.
Call for Action
I’m interested to see what’s we can do to improve the performance and invite you to discuss on the openSUSE-factory mailing list what to do. Contribution in benchmarking and figuring out bottlenecks is important as well.
So, whom does the problems hit – and how hard? So far, I see two culprits: The ext3 filesystem with barriers enabled and the Intel graphics driver. If you’re not using either, you’re on par with other recent distributions.
The ext3 filesystem regression can be worked around at the risk of filesystem integrity with disabling barriers. I doubt that I will hit this during normal desktop usage on my system.
The Intel issue has been discussed already at the openSUSE-factory mailing list and it was even suggested to not ship openSUSE 11.1 because of this. It hits some Intel graphics driver users quite card
and I wonder why I don’t see it on my machine. It might be better/worse on specific graphics chip.
If this issue is fixed with a new driver that works in our 11.1 setup, we will consider doing an update via our update repositories.
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