On 04/04/2011 05:52 PM, Charles G Waldman wrote:
>
> > Are any of xrootd team aware of
> > http://twiki.mwt2.org/bin/view/ITB/UltraLightKernel ? are there any (up
> > to date) recommendations based on this guys work?
>
> Hi -
Hi!
> I'm involved with both xrootd and the configuration of the Ultralight
> kernel.
great! you guys do an superb job (as far i seen in graphs :) )
> The major difference between the UltraLight kernel and the stock SL
> kernel is that the SL kernel is configured with preemption enabled,
> which is great for a user desktop, but not for a high-throughput
> data server.
and is this the only difference?
> We have found that on our test server (16-core server Dell 2950 with 6
> RAID6 shelves) with the SL kernel, under load, the "ksoftirqd" daemon
so the speed benchmark is done accessing all 6 raid6 arrays or just one
raid?
> takes up 100% CPU (this is a kernel thread involved in preemption),
> and the xrootd process is only able to deliver data at about 500MB/sec
> (about 50% of theoretical max on a on a 10Gb link).
>
> With the UL kernel, the "ksoftirq" CPU usage goes away completely, and
> xrootd is easily able to deliver data at wire speed (~1000MB/sc)
great news!!!
Thanks a lot!
Adrian
>
> - Charles
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