Mailinglist Archive: opensuse (908 mails)

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Re: [opensuse] Gobs of RAM?
On 06/03/2016 10:41 AM, Greg Freemyer wrote:
On Fri, Jun 3, 2016 at 1:15 PM, Lew Wolfgang <wolfgang@xxxxxxxxxxxxxxx> wrote:
Hi Folks,

Does anyone have experience with openSUSE and lots of RAM?
By lots, I mean as much as 6.1-TB of ECC RAM. Can Leap
effectively use that much memory?

If I'm current on my CPU knowledge, you will need a quad CPU server MB
with each core handling 1.5TB of the total RAM. Each quad CPU in turn
will likely have 15 or more cores. So you're looking at roughly 60
cores (120 hyperthreads)

That puts you into a serious NUMA design.

The linux scheduler used in Leap 42.1 is known to have serious issues
with NUMA efficiency

https://blog.acolyer.org/2016/04/26/the-linux-scheduler-a-decade-of-wasted-cores/

Note that post is less than 2 months old and says:

===
In our experiments, these performance bugs caused many-fold
performance degradation for synchronization-heavy scientific
applications, 13% higher latency for kernel make, and a 14-23%
decrease in TPC-H throughput for a widely used commercial database.
===

Given Leap 42.2 will be based on the already released 4.4 kernel, I
doubt if Leap 42.2 will have all of that corrected. You will need to
pay special attention to the Linux kernel you run and how many of the
scheduler bugs identified in that report are fixed.

Thanks for the info, Greg!

In this case, I was looking at four Xeon E7-8893v3 CPU's each of which has four
cores.
I guess with hyperthreading that would give 32-cores. The homegrown Python/C
code
they run is single-threaded, so possibly scheduling wouldn't be a significant
issue?

The mobo would be a Supermicro 8048B-TR4FT.

Interesting topic!

Regards,
Lew

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