From: David Jander <david.jander@protonic.nl>
To: linuxppc-embedded@ozlabs.org
Subject: Re: Kernel 2.6 on MPC8xx performance trouble...
Date: Mon, 31 Oct 2005 10:21:34 +0200 [thread overview]
Message-ID: <200510310921.34696.david.jander@protonic.nl> (raw)
In-Reply-To: <20051028153059.GC18915@logos.cnet>
On Friday 28 October 2005 17:30, Marcelo Tosatti wrote:
>[...]
> David,
>
> Do you have CONFIG_PIN_TLB enabled?
>
> If you do, please patch this in:
>
> http://www.kernel.org/git/?p=linux/kernel/git/marcelo/8xx-fixes;a=commitdif
>f;h=a41ba028534c45280170c05c23609ea84f34b38a
>
> And select DEBUG_PIN_TLBIE.
Ok, done that... no change.
I don't get any of those debug messages, so I guess that was not the problem.
I have made another test in the meantime, trying to check if cache is working.
The test is pretty simple: see how fast I can fill a block of memory whose
size is increasing by a power of two. You should expect to see a step-like
decrease in speed when surpassing the size of the data cache (4kbyte).
The results are very suspicious:
kernel-2.4:
Memsize 512 : 39.342773 Mbyte/s
Memsize 1024 : 41.871094 Mbyte/s
Memsize 2048 : 43.212891 Mbyte/s
Memsize 4096 : 40.117188 Mbyte/s
Memsize 8192 : 28.148438 Mbyte/s
Memsize 16384 : 28.484375 Mbyte/s
Memsize 32768 : 28.656250 Mbyte/s
Memsize 65536 : 28.687500 Mbyte/s
This looks quite healthy: above 4kbyte we see a clear drop in performance, so
we just learned that our data-cache is most probably 4kbyte in size, wow!
Kernel-2.6:
Memsize 512 : 21.033691 Mbyte/s
Memsize 1024 : 22.047852 Mbyte/s
Memsize 2048 : 22.601562 Mbyte/s
Memsize 4096 : 22.882812 Mbyte/s
Memsize 8192 : 23.007812 Mbyte/s
Memsize 16384 : 23.093750 Mbyte/s
Memsize 32768 : 23.125000 Mbyte/s
Memsize 65536 : 23.125000 Mbyte/s
No, sir, no cache detected !
Where do I have to look now?
Greetings,
--
David Jander
Protonic Holland.
next prev parent reply other threads:[~2005-10-31 8:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-28 6:57 Kernel 2.6 on MPC8xx performance trouble David Jander
2005-10-28 9:36 ` Roger Larsson
2005-10-28 10:57 ` David Jander
2005-10-28 18:44 ` Roger Larsson
2005-10-28 20:37 ` Wolfgang Denk
2005-10-31 9:31 ` David Jander
2005-10-28 15:30 ` Marcelo Tosatti
2005-10-31 8:21 ` David Jander [this message]
2005-10-31 12:58 ` Mark Chambers
2005-10-31 13:08 ` David Jander
2005-10-31 15:29 ` David Jander
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