Re: Hyper-Threading Vulnerability

Grant Coady
2005-05-13T19:46:28Z

On Fri, 13 May 2005 14:49:25 -0400, Scott Robert Ladd <lkml@coyotegulch.com> wrote:

>Alan Cox wrote:
>> HT for most users is pretty irrelevant, its a neat idea but the
>> benchmarks don't suggest its too big a hit
>
>On real-world applications, I haven't seen HT boost performance by more
>than 15% on a Pentium 4 -- and the usual gain is around 5%, if anything
>at all. HT is a nice idea, but I don't enable it on my systems.

P4-HT is great for winxp, a runaway process only gets half the CPU
resources, keeps the system responsive. I like HT for that reason,
perhaps that's what it was designed for? Hardware fix for msft 'OS' :o)

Recently on single AMD CPU box, 2.6.latest-mm, diff got stuck, no
disk activity, 100% CPU, started another terminal, recompiled kernel
with 8K stacks and rebooted, the whole time the unkillable 'diff'
was using just over 1/2 of resources. top showed all 1GB RAM in use,
no swap activity, nothing odd in /proc/whatever -- only happened once.

I suspected 4k stacks as only change before 'crash' was turning on
samba server day before, but I didn't trace 'problem' as it wasn't
really a crash. Impressive -- seeing 2.6 handling a stupid process,
business as usual for everything else. Haven't had a problem since
changing to 8K stacks. nfs, samba and ssh terminals on reiserfs 3.6
on via sata. May have had nvidia driver installed at the time, I
now load that only when X running (rare), mostly headless use.

--Grant.