Messages in this thread |  | | Subject | Re: The disappearing sys_call_table export. | From | Terje Eggestad <> | Date | 05 May 2003 15:23:39 +0200 |
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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. > > LD_PRELOAD >
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 PCI.
> > 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 mailto:terje.eggestad@scali.no Scali Scalable Linux Systems http://www.scali.com
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 NORWAY _________________________________________________________________________
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