[Nottingham] Spectre/Meltdown fixes *CLOBBER* HPC

[Martin]

Folks,

Well, I'm certainly not running any HPC but even for my meagre systems,
I've noticeably been hit last night with a backup over the network
running unexpectedly slowly:


Spectre/Meltdown fixes in HPC: Want the bad news or the bad news? It's
slower, say boffins

MIT Lincoln metalheads broke big iron so you don't have to... oh, you
still have to, don't you?

https://www.theregister.co.uk/2018/07/26/meldown_spectre_batters_hpc/

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... Network connection establishment – "With all mitigations enabled,
the mainline kernel is slowed down by approximately 15 per cent without
and 21 per cent with the User-Based Firewall..."

Disk access – "With all mitigations enabled, the mainline kernel is
slowed down by approximately 50 per cent on local disk and 33 per cent
on Lustre..."
#####


YEP! For the new backups times, I can well believe that!!

Ouch!


Noticed since the Gentoo kernel 4.17.9.

Good luck folks,

Cheers,
Martin