Text 21679, 43 rader
Skriven 2022-09-06 08:16:41 av Mike Miller (1:154/30)
  Kommentar till text 21675 av Benny Pedersen (2:230/0)
Ärende: xeon vs epyc
====================
Hello Benny!

01 Sep 22 12:08, you wrote to all:


 BP> Linux mx 5.15.63-gentoo-dist #1 SMP Thu Aug 25 12:40:44 -00 2022
 BP> x86_64 Intel(R) Xeon(R) CPU E5-2697 v4 @ 2.30GHz GenuineIntel
 BP> GNU/Linux Linux localhost 5.19.6-gentoo-dist #1 SMP PREEMPT_DYNAMIC
 BP> Wed Aug 31 18:48:13 -00 2022 x86_64 AMD EPYC 7642 48-Core Processor
 BP> AuthenticAMD GNU/Linux


 We've been switching over to Epyc boxes at work, and it's been a bit of a
nightmare, although mostly that's been due to software limitations.

 We started out with dual CPU 64-core Epyc CPUs, and ran into limitations with
applications that couldn't deal with 256 processors.  We had to manually pin
each thread/appliaction to a core / set of cores.

 We eventually switched over to purchasing single-CPU 64 core EPYC boxes, which
resolved our issues with CPU pinning for the most part.


However, every single EPYC box we're running has to have IOMMU disabled in
BIOS.  Otherwise, after about 3 months of running the servers will start
spewing "AMD-Vi: Completion wait loop timed out" errors. This will cause the
pcie devices to rapidly disable/re-enable, which knocks out networking.  We've
yet to nail down the actual cause of the issue, and it doesn't seem to matter
what kernel version we're running.   The odd thing is that it will happen in
short bursts,  groups of servers (usually assigned to the same application)
will start blowing up every hour or two, one after another. Not a fun thing
when I'm on call, because I swear it starts happening overnight every time. :D




Mike


... Dancers do it with rhythm.
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