HTT/SMP servers instability on 5.3-STABLE

[Kris Kennaway]

On Fri, Dec 10, 2004 at 05:58:06AM -0600, klr at 6s-gaming.com wrote:
> Hi,
> 
> I have a Dual Xeon 2.4 and a Dual Xeon 2.8 servers running with
> HyperThreading, ACPI, and SMP enabled.
> 
> The 2.8 server won't stand for more than 5 days without crashing, and the
> 2.4 server was up 30 days crashed, now was up 12 days, and crashed.
> 
> I didn't have a debugging kernel, I'll be building one when the datacenter
> reboots the server. I also don't have any panic messages.. I have,
> however, a few questions:
> 
> - machdep.cpu_idle_hlt - I've seen a lot on google about this sysctl, but
> still don't fully understand it. What does this sysctl really changes?

It doesn't put the CPU to sleep in the idle loop, which can cause a
performance loss in some cases, but also uses less power and generates
less heat.

> - HyperThreading - Do I really have a performance increase with HTT turned
> on?

It depends on the workload you're doing.  Try it and see.  

> I've heard it can penalize performance because the scheduler isn't
> optimized for logical CPUs.  Does having HTT enabled impacts the stability
> of the system?

No.

> - ACPI - I'll be disabling ACPI along with HTT to see if the server
> doesn't crash for awhile. Is ACPI on 5.3-STABLE (around November 1st, it
> was pre-release) still a problem?

Only if the problem is with your machine, i.e. if you have a buggy
BIOS.  Don't discount this; look for an update from your vendor.

> Last but not the least, my 5.3-STABLE version is from a few days before
> the release. Since I had created a few jails by then, I didn't upgrade the
> system to use the -RELEASE. Was there any last-standing problem a few days
> before the release that could be causing my instability problems?

It's quite possible.  The release was made when it was and not earlier
precisely because there were bugs in earlier versions.

Kris
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