2.5 or 2.4 kernel profiling

[Brian Ford]

On Mon, 11 Dec 2000, Graham Stoney wrote:

> Hi Brian,
>
> On Thu, Dec 07, 2000 at 12:11:07PM -0600, Brian Ford wrote:
> > I am trying to do some kernel profiling on my EST8260 to determine the
> > bottle neck in TCP and UDP thruput, but I can't seem to get any profile
> > information.
>
> When I first attempted a similar thing with the 2.2 kernel on our 855T based
> board, I found that the trivial do_profile routine needed to collect data for
> /proc/profile kernel profiling wasn't implemented for the ppc architecture.
> As far as I can see, it still isn't implemented on linux-2.4.0-test11, but it
> is in the linuxppc_2_3 tree at http://www.fsmlabs.com/linuxppcbk.html .
> I really wish the seperate architecture maintainers had got together to
> eliminate all the duplicated do_profile functions like I did in my 2.2 patch
> at:
>     http://members.nbci.com/greyhams/linux/patches/2.2/profile.patch
>
> Unfortunately I guess it was easier for the PPC guys to just copy the
> do_profile function (yet again!) like everyone else did.  Oh well, maybe in
> 2.5...
>
Thanks.  I did get it to work with the bitkeeper sources.  My problem was
that the grep command that produced the System.map file didn't get along
with Solaris grep.

I agree with you about the profiling stuff.  Did you post this idea to the
main kernel mailing list?  Maybe that would be the place to tackle this
issue.

> Back to TCP, I found I could improve raw TCP throughput by 15-20% on the 855T
> by DMAing received data directly into the kernel socket buffers.  The
> improvement in performance from eliminating the extra copy between the ring
> buffer and socket buffer isn't staggering, since the CPU still needs to do
> a pass through the data to calculate the IP checksum, which unfortunately the
> 855T's FEC can't do for me.  Nevertheless, it does make things a little faster
> and I would imagine a similar technique would work on the 8260; you can get a
> feel for what is involved from my 2.2 FEC speedup patch at:
>     http://members.nbci.com/greyhams/linux/patches/2.2/fecdmaskb.patch
>
Thanks.  I had already hacked something like this together.  It would be
great to finalize these and get them into the real sources.

I also turned checksumming off for testing purposes.  It helped some, but
I think my bottle neck is that I can't get the bus to run faster than 33
Mhz reliably.  If I could get the bus clocked at what it is rated, I might
be better off.

I don't think the 8260 CPM can do the checksums either.  Pitty.  It seems
like there is plenty of power in there.

--
Brian Ford
Software Engineer
Vital Visual Simulation Systems
FlightSafety International
Phone: 314-551-8460
Fax:   314-551-8444


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