Re: 2.2.18Pre Lan Performance Rocks!

Jeff V. Merkey
2000-10-30T09:24:18Z

On Mon, Oct 30, 2000 at 11:27:04AM +0100, Ingo Molnar wrote:
>
> On Mon, 30 Oct 2000, Jeff V. Merkey wrote:
>
> > For example, if you put a MOV EAX, CR3; MOV CR3, EAX; in a context
> > switching path, on a PPro 200, you can do about 35,000 context
> > switches/second
>
> in 2.4 & Xeons we can do more than 100,000 context switches/second, and
> that is more than enough. But the point is: network IO performance does
> not depend on context switching speed too much. Also, in Linux we are
> using global pages which makes kernel-space TLBs persistent even across
> CR3 flushes.

This is putrid. NetWare does 353,00,000/second on a Xenon, pumping out
gobs of packets in between them. MANOS does 857,000,000/second. This
is terrible. No wonder it's so f_cking slow!!!

>
> > [...] There's also the use of segment registers all over the place to
> > copy from kernel to user and user to kernel space memory. [...]
>
> we do not use the fs segment register for user-space copies anymore,
> neither in 2.2, nor in 2.4. You must be reading old books and probably
> forgot to cross-check with the kernel source? :-)

ds: and es: are both used in copy-to-user and copy-from-user and they get
reloaded.

>
> > [...] Having the fast paths you mention does help a lot, but it's the
> > fact that this goes on at all that will make it tough to walk into a
> > NetWare shop with Linux and rip out NetWare servers and replace them
> > unless we look at a NetWare vs. NetLinux (that's what we call it! a
> > NetWare-like Linux platform).
>
> the worst thing you can do is to mis-identify performance problems and
> spend braincells on the wrong problem. The problems limiting Linux network
> scalability have been identified during the last 12 months by a small
> team, and solved in TUX. TUX is a fileserver, it shouldnt be alot of work
> to enable it for (TCP-only?) netware serving. It's *done*, Jeff, it's not
> a hypotetical thing, it's here, it works and it performs.
>

NetWare is here too, and it handles 5000+ file and print users, Linux does not.
Let's fix it. I know why NetWare is fast. Let's apply some of the same
principles and see what happens. Love to have you involved.

> Ingo