FC4 and xen0 performance

[Dave Jones]

On Wed, Apr 06, 2005 at 07:06:17AM -0400, Alan Cox wrote:
 > On Tue, Apr 05, 2005 at 11:53:33AM -0700, Jeffrey Buell wrote:
 > > results are pretty ugly compared to a 2.6.1 install. FC4 ranges from 1.5X to
 > > 20X slower, while xen0 is about 2X to 6X slower.  Is this expected? I'm
 > > looking for configuration differences now, but I'm wondering if anybody can
 > 
 > The fork ones are expected yes. The newest kernels have four level page tables
 > and while this allows for huge 64bit systems it has a cost and there is 
 > optimisation work left to do.

They should be getting collapsed away back to 2/3-level PTEs by the compiler
in the current builds. I thought that got fixed for 2.6.12-rc1.
If it missed it, theres a .12-rc2 update pending, but that won't hit
until post -test2 now.

 > I've not checked the kernel config options but if you look at the src.rpm you
 > can see what debug is enabled

Slab debug is the only thing left on thats really a performance hit.

		Dave