[Beowulf] [upgrade strategy] Intel CPU design bug & security flaw - kernel fix imposes performance penalty

[Jörg Saßmannshausen]

Dear Chris,

the first court cases against Intel have been filed:

http://www.spiegel.de/netzwelt/web/spectre-meltdown-erste-us-verbraucher-verklagen-intel-wegen-chip-schwachstelle-a-1186595.html

http://docs.dpaq.de/13109-show_temp.pl-27.pdf

http://docs.dpaq.de/13111-show_temp.pl-28.pdf

http://docs.dpaq.de/13110-07316352607.pdf

So, lets hope others are joining in here to get the ball rolling.

Don't get me wrong here, this is nothing against Intel per se. However, and 
here I am talking wearing my HPC hat, a performance decrease of up to 30% is 
simply not tolerable for me. I am working hard to squeeze the last performance 
out of the CPU and using highly optimised libraries and then the hardware has 
a flaw which makes all of that useless. I am somewhat surprised that this has 
not discovered earlier (both bugs I mean). 

I am sure it will be interesting to see how it will be patched and what the 
performance penalty will be here. 

All the best

Jörg

Am Samstag, 6. Januar 2018, 03:27:33 GMT schrieb Christopher Samuel:
> On 05/01/18 10:48, Jörg Saßmannshausen wrote:
> > What I would like to know is: how about compensation? For me that is
> > the same as the VW scandal last year. We, the users, have been
> > deceived.
> 
> I think you would be hard pressed to prove that, especially as it seems
> that pretty much every mainstream CPU is affected (Intel, AMD, ARM, Power).
> 
> > Specially if the 30% performance loss which have been mooted are not
> > special corner cases but are seen often in HPC. Some of the chemistry
> > code I am supporting relies on disc I/O, others on InfiniBand and
> > again other is running entirely in memory.
> 
> For RDMA based networks like IB I would suspect that the impact will be
> far less as the system calls to set things up will be impacted but that
> after that it should be less of an issue (as the whole idea of RDMA was
> to get the kernel out of the way as much as possible).
> 
> But of course we need real benchmarks to gauge that impact.
> 
> Separating out the impact of various updates will also be important,
> I've heard that the SLES upgrade to their microcode package includes
> disabling branch prediction on AMD k17 family CPUs for instance.
> 
> All the best,
> Chris