Hi,
I am happy to report that I have now uploaded all the code necessary to use
PEBS on Intel Core, Atom, and Nehalem. That includes PEBS-LL on Nehalem
which is used to sample where cache misses occur.
What you need:
- latest libpfm sources from CVS
- latest pfmon sources from CVS
- perfmon2 2.6.30 from GIT
git clone
git://git.kernel.org/pub/scm/linux/kernel/git/eranian/linux-2.6.git
Make sure you enabled 'Unified PEBS'
This kernel includes a unified PEBS sampling format which supports Netburst,
Core, Atom, and Nehalem. You must insert the module perfmon_pebs_smpl
(or compile in the code).
Next, to use PEBS, you can simply do:
pfmon --smpl-module=pebs --smpl-compact --with-header -einst_retired:any_p \
--long-smpl-period=2400000 ...
Not all events support PEBS. In --smpl-compact mode, each line
contains a PEBS
sample.
To collect cache misses on Nehalem, you can do:
pfmon --smpl-module=pebs-ll -e MEM_INST_RETIRED:LATENCY_ABOVE_THRESHOLD \
--ld-lat-threshold=4 --long-smpl-periods=2000 --smpl-compact
--with-header ...
You must use the MEM_INST_RETIRED:LATENCY_ABOVE_THRESHOLD to activate this
HW feature.
Each line contains a PEBS record, including the cache miss
information. The ld-lat parameter
is the minimal threshold for the miss latency. Only misses >=
threshold are captured. It must
be at least 4. 4 cycles is the L1D hit latency. For each captured
miss, you get an instruction addr,
data addr, miss latency, source of the data (where did it come from,
refer to Intel documentation).
It is important to understand that the instruction addr does NOT point
to the load instruction but
ALWAYS to the next dynamic instruction, i.e., the whole state is
recorded at retirement of the load.
On Mon, Oct 5, 2009 at 1:55 AM, Carole Wu <cwu...@gmail.com> wrote:
> Hello,
>
> I'd like to collect information about my workload, running on Nehalem, using
> PEBS, so I use the following command.
>
>>> pfmon -e MEM_INST_RETIRED:LATENCY_ABOVE_THRESHOLD --ld-lat-threshold=1
>>> --long-smpl-periods=2000 --short-smpl-periods=200 ./mcf_base inp.in
>>> load latency threshold not yet supported
> However, the response seems to suggest that my machine does not currently
> support PEBS? Is it true, or am I not setting parameters correctly?
>
> Any help is greatly appreciated.
>
> Carole
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