Re: Can context switches be faster?

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John Richard Moser wrote:

Linux ported onto the L4-Iguana microkernel is reported to be faster
than the monolith[1]; it's not like microkernels are faster, but the
L4-Iguana apparently just has super awesome context switching code:

   Wombat's context-switching overheads as measured by lmbench on an
   XScale processor are up to thirty times less than those of native
   Linux, thanks to Wombat profiting from the implementation of fast
   context switches in L4-embedded.

The Xscale is a fairly special beast, and it's context-switch times are pretty slow by default.

Here are some context-switch times from lmbench on a modified 2.6.10 kernel. Times are in microseconds:

cpu		clock speed	context switch	
pentium-M	1.8GHz		0.890
dual-Xeon	2GHz		7.430
Xscale		700MHz		108.2
dual 970FX	1.8GHz		5.850
ppc 7447	1GHz		1.720

Reducing the Xscale time by a factor of 30 would basically bring it into line with the other uniprocessor machines.

Chris
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