Re: [PATCH] reorganized per-CPU data

From: Andi Kleen (
Date: Fri Jun 16 2000 - 17:38:02 EST

On Fri, Jun 16, 2000 at 02:26:29PM -0700, Dimitris Michailidis wrote:
> New in this version:
> - ported to -test1
> - some more code has been converted to use the new scheme
> - on MP systems we allocate only as many PDAs as we need.
> Given that these structures are large (>2K each, larger with IPv6 enabled)
> the allocation change above can save substantial space on MP systems. On a
> 4P box space savings amount to more than 79K, .text savings alone exceed 5600
> bytes (including small savings in the system call and IRQ paths in entry.S ;-)

Cool :-)

> Andi Kleen wrote:
> > Just an ugly problem is the Config dependent layout of the pda data
> > and module binary compatibility. Maybe it would be possible to tag
> > some magic symbol with its size and export it, making modules reference
> > it ?
> These issues are still present. I don't think exporting the size of a pda is
> safe, you might be able to get the same size with different configurations.
> Maybe exporting the offsets of optional fields?

MODVERSIONS uses a special program that generates function signatures. That
could be probably extended to the PDA. One easy way would be to store
a md5 hash of the preprocessed PDA include file.


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