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Re: performance loss on real time linux

Michael Ströder wrote:
Pierangelo Masarati wrote:
run a simple test using OpenLDAP 2.3.28 running on Linux 2.6.17 with
RTAI, compared to the stock kernel f the distribution
Do you mean stock 2.6.15?
No, I have no idea.
- searching for the same entry, after it's in cache, requires ~0.008s w/
RTAI, and ~0.080s w/o RTAI (ten times longer! It's a slightly different
kernel, but running on exactly the same machine, [..]

Are you sure there haven't been any significant changes to the scheduler
between these two kernel versions anyway? Also distributions most times
ship with a patched kernel. So exact comparison should be done with a
vanilla kernel and the very same kernel with RTAI.
I concur. The point is that to apply RTAI patch we need an official kernel release (usually the latest, or occasionally the latest-but-one), but usually we only rebuild it with the RTAI patch, and not without (there's no need to). So, just to have an idea of how OpenLDAP behaved with the RT scheduling, I simply ran the same tests with the distribution's kernel. The distribution was Ubuntu, but I don't remember the version or any other detail. Only in case of dramatically slower response I would have checked more carefully those details.