From mboxrd@z Thu Jan  1 00:00:00 1970
From: mulyadi.santosa@gmail.com (Mulyadi Santosa)
Date: Sun, 12 Feb 2012 18:46:42 +0700
Subject: How to measure performance inside Kernel?
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Hi Peter...

On Sat, Feb 11, 2012 at 20:57, Peter Senna Tschudin
<peter.senna@gmail.com> wrote:
> Graeme,
>
> I found a problem on my code. I was calling kmalloc() only once for
> both portions of code. The result is that the first loop that accessed
> the memory was finding some penalty. Now I'm calling independent
> kmalloc for each test.

Sorry for jumping in the mid of discussion :)

I read your code and I think kmalloc can be streamlined here. I
recommend that kmalloc() allocate total memory needed to handle whole
q->buf[] array. something like (CMIIW):

q->buf=kmalloc(sizeof(struct vb_buffer)*q->num_buffers,GFP_KERNEL)

then access q->buf[1], q->buf[2] etc.

This way, AFAIK, you will likely get not only virtually continous
pages, but also physical continous pages. And that will ease
prefetching into L1/L2 cache.

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com