Re: [gentoo-amd64] Re: SMP

[Mihir Sevak]

Duncan,
  I thank you very much. Being little specific about my objective is i am
thinking of an
embedded system which can give me a very high processing speed. In other
words i wouldn't have much memory or other resources. Also i have to take
charge of the process scheduling as much as i can. So if i understand
correct i would be better off by
looking into kernal code rather than using other scheduling utilitis.
right???

Thanks.


On 5/26/06, Duncan <1i5t5.duncan@×××.net> wrote:
>
> "Mihir Sevak" <mihir.sevak@×××××.com> posted
> 48fcf8860605260703m2264be8hcd5a5fc9d43c86dd@××××××××××.com, excerpted
> below, on  Fri, 26 May 2006 10:03:24 -0400:
>
> > i am using C as a programming language. I have an AMD 64 dual core
> > system. Is there any way i can take charge of those two processors and
> > command them which thread should run on which processor??? I am prepared
> > with scheduling mechanism but only thing i am lacking is how to take
> > charge and decide that which processor should run which thread.
>
> I'm rather far from an expert in the field, but AFAIK, you use kernel
> scheduling domains for that, and configure your app to use a specific
> scheduling domain.  AFAIK, the functionality is fairly new, and you'll
> need 2.6.16 or even the 2.6.17-rcs, plus some special user side utilities
> to configure and manage the domains, to get it working.
>
> Automatic kernel SMP scheduling normally does a pretty good job, noting of
> course that on some hardware, some chipset elements may be connected to
> only one of the CPUs (tho that shouldn't be a problem for dual-core), and
> the various costs of switching between cores on the same CPU, as opposed
> to different CPU/sockets, as opposed to different hosts (in a clustering
> environment), what with local vs remote memory and cache coherency and the
> like.  Specifying a CPU/core is now possible using the special tools
> mentioned above, but it's seldom worth the trouble, and can actually be
> worse.  It may be better to tweak the various tweakables exposed by the
> kernel for its automated scheduling, changing how it chooses to switch
> CPUs if one is busier than the other.
>
> FWIW, I have a dual Opteron system here, single-cores.  I expect to be
> upgrading later this year to dual-cores, for a 4-core system on dual
> socket-940.  I've generally been fairly happy with the kernel's scheduling
> as-is, allowing for when I'm running single-threaded apps that /can't/
> divide the work.  If the app is multithreaded, or I'm running several apps
> in parallel, the kernel generally does a pretty good job of keeping things
> balanced.  Back when I had a single-disk system, that was often the
> bottleneck.  However, with a 4 disk RAID system (kernel-RAID, RAID-6 for
> most of it, RAID-0 for the performance critical redundancy unneeded stuff,
> RAID-1 for /boot) and 8 gig of memory, the bottleneck is again usually the
> CPUs, thus the planned upgrade to 2 by dual-cores later this year.
>
> Of course, that's for personal desktop/workstation use.  If I were running
> something less general purpose, say a big database server or the like,
> there would indeed be reason to think about specific tuning including
> possibly confining some tasks to specific CPUs.
>
> --
> Duncan - List replies preferred.   No HTML msgs.
> "Every nonfree program has a lord, a master --
> and if you use the program, he is your master."  Richard Stallman
>
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> gentoo-amd64@g.o mailing list
>
>


-- 
"How can anything be impossible when impossible itself says I M Possible???"
Mihir