Today Dell released an BIOS update that affects many of our Dell PowerEdge 12th Generation servers. The BIOS update includes a change which can improve system performance with many Linux distributions.
First, a little background: Systems with NUMA architecture have memory that is connected to a particular CPU socket. So, on systems with more than one CPU socket, this means that each CPU can access some memory (the memory connected directly to it) faster than other memory. This isn't new--this architecture has been used in previous generations of Dell servers as well as our new 12th Generation servers. ACPI tables provided by system firmware (BIOS) provide the details to the operating system so that it can make sure that the right memory is used by the right CPU, to minimize memory access times.
In our 12th Generation servers, each PCI device is also "closer" to one of the CPUs in the system (and also closer to the memory connected to that CPU), unlike our previous generations of servers. With the BIOS update released today, this PCI proximity information is also provided to the operating system, so that it can ensure that the optimal CPUs are talking to the PCI devices when they need attention, and to make sure the memory with the fastest access times is assigned for use by the PCI devices.
This can increase performance when using Linux distributions, such as Red Hat Enterprise Linux 6 and Novell's SUSE Linux Enterprise Server 11. Note that this change will only affect systems with at least two occupied CPU sockets, and node interleaving must also be disabled in BIOS setup. (Node interleaving masks the effect of certain CPUs and PCI devices being closer to certain memory, which is useful with older operating systems that don't understand NUMA architecture.)
Thank you for the update