Re: [Qemu-devel] [PATCH v6 01/22] instrument: Add documentation

[Lluís Vilanova]

Emilio G Cota writes:

> On Mon, Sep 25, 2017 at 21:03:39 +0300, Lluís Vilanova wrote:
>> I know it's not exactly the same we're discussing, but the plot in [1] 
>> compares
>> a few different ways to trace memory accesses on SPEC benchmarks:
>> 
>> * First bar is using a Intel's tool called PIN [2].
>> * Second is calling into an instrumentation function on every executed memory
>> access in QEMU.
>> * Third is embedding the hot path of writing the memory access info to an 
>> array
>> into the TCG opcode stream (more or less equivalent to supporting filtering;
>> when the array is full, a user's callback is called - cold path -)
>> * Fourth bar can be ignored.
>> 
>> This was working on a much older version of instrumentation for QEMU, but I 
>> can
>> implement something that does the first use-case point above and some 
>> filtering
>> example (second use-case point) to see what's the performance difference.
>> 
>> [1] https://filetea.me/n3wy9WwyCCZR72E9OWXHArHDw

> Interesting! Unfortunately, this URL gives me a 404.

Ok, I've uploade it somewhere else:

  https://people.gso.ac.upc.edu/vilanova/mtrace.pdf

There's also another one that simply counts the number of memory accesses, using
the same three approaches:

  https://people.gso.ac.upc.edu/vilanova/mcount.pdf

Cheers,
  Lluis