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SubjectRe: The disappearing sys_call_table export.
On Mon, 2003-05-05 at 13:16, Alan Cox wrote:
> On Llu, 2003-05-05 at 10:33, Terje Eggestad wrote:
> > 1. performance is everything.
> Then you can live with building custom patched kernels

If there was numerous issues, sure. But every time we get to the point
where it seem that that is necessary we find a workaround.
Right now, this is the ONLY issue we got..

> > 2. We're making a MPI library, and as such we don't have any control
> > with the application.

IN general LD_PRELOAD is fun for testing and academic programs, but not
for production code.

In specific you run into a problem with how fortran 90 compilers do
dynamical arrays. It's very compiler dependent.

> > 3c. It's therefore necessary for HW to access user pages.
> Like TV cards do. That isnt hard

nobody said it is.

> > 4. In order to to 3, the user pages must be pinned down.
> > 5. the way MPI is written, it's not using a special malloc() to allocate
> > the send receive buffers. It can't since it would break language binding
> > to fortran. Thus ANY writeable user page may be used.
> Well not all the pages are guaranteed DMAable, so I guess you already
> lost.

Nope. The drivers test to see if the page is DMAable, and do a copy if
necessary. Most of the high performance interconnects NIC's do 64 bit

> > 10. kernel patches are impractical, I must be able to do this with std
> > stock, redhat, AND suse kernels.
> So you want every vendor to screw up their kernels and the base kernel
> for an obscure (but fun) corner case. Thats not a rational choice is it.
> You want "performance is everything" you pay the price, don't make
> everyone suffer.

No! I don't disagree with removing the export of the syscall_table!

I just want the "proper mechanism" indicated by Arjan in the changelog.
Pls read this thread. There are legitimate uses to having syscall
hooks/notifications, either you think mine is or not.


Terje Eggestad
Scali Scalable Linux Systems

Olaf Helsets Vei 6 tel: +47 22 62 89 61 (OFFICE)
P.O.Box 150, Oppsal +47 975 31 574 (MOBILE)
N-0619 Oslo fax: +47 22 62 89 51

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