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Date: Thu, 11 Oct 2007 11:06:08 +0930
From: David Newall <david@...idnewall.com>
To: Russ Dill <russ.dill@...il.com>
CC: linux-kernel@...r.kernel.org
Subject: Re: [OT] Argument with an OS professor over profile=3
Russ Dill wrote:
> I've been having a back and forth going for a while with my TA and OS
> professor on the meaning of profile=3 and have been unable to convince
> either of them. The basic question is if profile=3 is passed to kernel
> with an 8MB text section, how big is the allocated profile buffer. His
> answer is 1MB....
>
> if (prof_shift) {
> unsigned int size;
> /* only text is profiled */
> prof_len = (unsigned *) &_etext - (unsigned *) &_stext;
>
You stipulated 8MB text, but this calculates in unsigned ints, so
prof_len = 2M.
> prof_len >>= prof_shift;
>
This gives 250K (divide by 8).
> size = prof_len * sizeof(unsigned int) + PAGE_SIZE-1;
>
Finally, size is 1MB (250K x 4).
> prof_buffer = (unsigned int *) alloc_bootmem(size);
> }
>
I'm with your Prof. Perhaps you missed that prof_len counts integers,
not bytes.
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