Very Computer

Does valgrind do this?  I've heard lots about it, but never used it.

Quote:> I thought maybe I should write a kernel module to watch memory accesses,
> but I'm guessing that if the word of data which is being read/written is
> already in memory (which it probably will be, most of the time), then the
> OS will never see the memory request (as a page-fault exception will never
> be raised).

Right, the kernel is only activated on an exception, interrupt, or
system call, and does not monitor specific user instructions (and
really has no reason to, and to actually implement something like
this would probably not be trivial).

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It does.
That's probably OP's best hope ...

Quote:> > I thought maybe I should write a kernel module to watch memory accesses,
> Right, the kernel is only activated on an exception, interrupt, or
> system call, and does not monitor specific user instructions (and

If the kernel watched every memory access of every user process,
all your programs would slow down to a crawl. This approach is
simply unfeasible for any realistic amount of code.

Cheers,
--
In order to understand recursion you must first understand recursion.

[reformatted for readability]

I've been fiddling around with valgrind but I can't seem to figure out
how to actually get it to do this - the closest I've come is using
"--skin=cachegrind". As it's simulating cache hits/misses, it must
(internally) have a list of all the reads/writes done by the processor -
but how do I get at this information?

From the docs, I see that cachegrind produces a cachegrind.out.pid file,
of "line-by-line information" - is this the raw cache information (it
doesn't really look like it)? How do I interpret it if it is?

Thanks for everyones help.

Steve

valgrind has extensive design documentation included. Perhaps you should
read it?

-Andi

: Hi, I'm wanting to get a list of all memory reads/writes performed by an
: application.

: Can anyone advise me on where I would start, to achieve this? I took a
: look around freshmeat.net for "memory trace" software, but it all seems to
: be stuff to look for leaks, and just tells you when a malloc or free is
: performed (I want individual reads/writes, so for example if "LD  r1,
: 0(r2)" was performed, I'd get as an output something like "read
: <address_in_r2>").

Do you realize that memory acesses are quite frequent? It is not much
more expensive to get just a list of all intructions executed by your
program. In fact I think that Bochs is closest to what you want: it
interpetts all instuctions in your program and have some support to
trigger special actions for each instucton. But, I am affraid you will
have to do some hard work (and in "tracing mode" your program will
run at say 1/1000 normal speed).
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