TSC warp, Threads

ASSI Stromeko at nexgo.de
Thu Mar 11 09:46:46 UTC 2021

Hal Murray via devel writes:
> Does anybody have access to server class systems?

Not with bare metal Linux at the moment…

> I'm trying to setup a test environment for the thread work.  Dell high end 
> workstations use Xeon chips.  I have a T5610, but it has TSC warp so doesn't 
> use the TSC for timekeeping.  That's not fatal, but it's annoying and screws 
> up trying to get timing for what a real system would get.

That's an IvyBridge I think, you will want Haswell or later.

> As far as I can tell, there isn't a features flag for this feature.

There used to be stable_tsc (don't remember which kernel version and
whether it was reliable), now there are nonstop_tsc, tsc_adjust and
tsc_reliable (and probably a few more I haven't seen yet)… Some of these
are invalid (or get removed) when you run under a Hypervisor.

> Ideally, I'd like to find a workstation (quieter than servers) that doesn't 
> have this bug/feature and is old enough so I can get a refurbished system at a 
> reasonable price.

Haswell and later are OK (Xeon v3 and up) AFAIK, although there may be
interactions with microcode / BIOS and how deep a sleep state gets
allowed.  So if you want to stick with the Xeon EP Haswell line
(Grantley chipset) that leaves you with Dell T5810, T7810; Lenovo P500,
P700, HP Z440, Z840, Fujitsu M740, R940 (single / dual socket
respectively).  These all have "interesting" configuration rules and are
picky about the memory (some more so than others), so if you plan to
upgrade the memory or stick in other hardware you'll need to know
exactly what is already in there or throw the existing stuff out and put
in a new kit with the correct configuration.  You can easily exceed the
cost of the initial box that way, so it pays to hunt for a refurb that
is configured exactly as you want it even if it takes longer.  Some of
these can take Broadwell EP, although if you don't care about AVX512 and
slightly enhanced memory bandwidth it does not make a lot of a
difference either way.  I think the Lenovo should be the quietest of the
bunch if otherwise the same configuration, relatively speaking.  I
probably wouldn't want to have any of these on my desk if they run full
throttle and some of them not under my desk either and that is before
adding a graphics card…

+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptation for Waldorf Blofeld V1.15B11:

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