Re: RHEL 3

We're currently using RHEL3 U8 on mostly dual-core, dual-socket (but 
also lots of dual-core, quad- and octo-socket) Opteron systems with no 
problems at all using the SMP kernel.

So at least for AMD architectures, I can confirm that multicore support 
is there.  What isn't is ccNUMA suport.  Even in RHEL4 it isn't really 
there.  The kernel "supports" it, but but multi-core chips, the RHEL3 
kernel falls apart when trying to determine what memory is mapped to 
which CPU.  RHEL4 is marginally better, but frankly NUMA support should 
be simply disabled until RHEL5, where it has actually been implemented 
properly.

Use "numa=off" on the kernel command line, and in the BIOS of your 
systems set Node Interleaving to "on" or "auto", and turn off the ACPI 
SRAT table.  This will set your system up as a "normal" SMP system, 
which RHEL3 can get very good performance from.

Paul Krizak                         5900 E. Ben White Blvd. MS 625
Advanced Micro Devices              Austin, TX  78741
Linux/Unix Systems Engineering      Phone: (512) 602-8775
Silicon Design Division             Cell:  (512) 791-0686


Majumder, Rajib wrote:
> Hi,
> 
> I am wondering if RHEL 3 (based on 2.4.21 kernel but RH claims they 
> backported lot of 2.6 kernel's feature into it) supports Multi-Core and 
> Hyperthreaded CPUs.
> 
> I am specifically looking to clarify the following on RHEL 3 (containing 
> the RH-engineered 2.4.21 kernel):
> 
> 1) Is the CPU-scheduler multi-core/hyperthreading aware?
> 2) Is it aware ccNUMA multi-core CPU?
> 
> Any input is appreciated.
> 
> Thanks
> 
> Rajib
> 
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