Re: [PATCH v4 0/3] perf alpha: Decode ProfileMe samples

[Namhyung Kim <namhyung@kernel.org>]

Hello,

On Tue, Nov 10, 2026 at 08:31:02PM +0100, Magnus Lindholm wrote:
> Hi all,
> 
> On Wed, Nov 4, 2026 at 7:53 PM Matt Turner <mattst88@gmail.com> wrote:
> >
> > The Alpha kernel series "alpha/perf: add ProfileMe sampling" adds
> > ProfileMe sampling to the Alpha cpu PMU. Each ProfileMe sample carries
> > the profiled instruction's PMPC and its I_STAT and PCTR_CTL status as
> > PERF_SAMPLE_RAW data, which says whether the instruction retired,
> > whether it trapped and why, whether it was a mispredicted branch,
> > stalled before map, or was killed on a wrong path, and what PCTR1
> > counted while it was in flight:
> >
> >   https://lore.kernel.org/r/20261104-alpha-profileme-v6-0-63362e9290a3@gmail.com
> >
> > This series is the perf tool side. Patch 1 decodes the raw data in perf
> > report -D and perf script -D, as is done for AMD IBS. It copies the new
> > uapi header from the kernel series into tools/arch, so it should wait
> > until that header is merged. Patch 2 adds a script that sums the status
> > by symbol or by instruction, in the style of DCPI. Patch 3 gives perf
> > mem a ProfileMe event, as the kernel series reports the DTB hits and
> > misses of loads and stores in the data source.
> >
> > To try it, with the kernel series applied:
> >
> >   perf record -R -e cpu/instructions,profileme/ -- ./workload
> >   tools/perf/python/alpha-profileme.py --pc
> >
> > I tested this on an AlphaServer ES47 (EV7). Sampling a loop whose
> > branch tests random data reports that branch mispredicted in 21% of its
> > samples, and 0% with sorted data. As a normal user, perf mem record on
> > a loop that loads one word from each page reports the load's DTB hits
> > and misses.
> >
> > Signed-off-by: Matt Turner <mattst88@gmail.com>
> > ---
> > Changes in v4:
> > - Patches 1 and 2: ignore TRP, and MIS and the trap type with it, for
> >   an instruction killed before it was mapped, as the kernel series
> >   does. Thanks to Ian Rogers.
> > - Patch 2: record cpu/instructions,profileme/ in the example, as a
> >   precise event now samples only retired instructions, which leaves
> >   the killed% and invalid% columns at 0. Thanks to Ian Rogers.
> > - New patch 3: add a perf mem event for Alpha, cpu/cycles,profileme/.
> >   Suggested by Ian Rogers.
> > - Link to v3: https://patch.msgid.link/20261102-perf-alpha-profileme-v3-0-4bf6e1dda733@gmail.com
> >
> > Changes in v3:
> > - Patch 1: silence -Wpacked around the uapi header, which breaks the
> >   build where __u64 is 4-byte aligned, such as sh4.
> > - Patch 2: only read raw data from cpu PMU events, as a tracepoint's
> >   payload can pass for ProfileMe status. Thanks to Magnus Lindholm.
> > - Patch 2: print a table for each thing PCTR1 can count, so that mixing
> >   events no longer averages unrelated values. Thanks to Magnus Lindholm.
> > - Link to v2: https://patch.msgid.link/20261030-perf-alpha-profileme-v2-0-9ce2f0b0e622@gmail.com
> >
> > Changes in v2:
> > - Patch 1: copy the raw data out of the sample and convert it from
> >   little endian, so that it decodes on strict-alignment and big-endian
> >   hosts.
> > - Patches 1 and 2: follow the new 28-byte struct alpha_profileme_sample
> >   from kernel v2.
> > - Link to v1: https://patch.msgid.link/20261028-perf-alpha-profileme-v1-0-f46c1938d001@gmail.com
> >
> > ---
> > Matt Turner (3):
> >       perf alpha: Decode ProfileMe raw samples
> >       perf python: Add alpha-profileme.py
> >       perf alpha: Add perf mem support
> >
> >  tools/arch/alpha/include/uapi/asm/perf_event.h |  31 +++++
> >  tools/perf/Documentation/perf-mem.txt          |   3 +
> >  tools/perf/arch/alpha/Build                    |   2 +-
> >  tools/perf/arch/alpha/util/Build               |   2 +
> >  tools/perf/arch/alpha/util/mem-events.c        |  17 +++
> >  tools/perf/arch/alpha/util/mem-events.h        |   7 +
> >  tools/perf/arch/alpha/util/pmu.c               |  11 ++
> >  tools/perf/check-headers.sh                    |   1 +
> >  tools/perf/python/alpha-profileme.py           | 178 +++++++++++++++++++++++++
> >  tools/perf/util/Build                          |   1 +
> >  tools/perf/util/alpha-sample-raw.c             | 156 ++++++++++++++++++++++
> >  tools/perf/util/sample-raw.c                   |   2 +
> >  tools/perf/util/sample-raw.h                   |   2 +
> >  13 files changed, 412 insertions(+), 1 deletion(-)
> > ---
> > base-commit: 4626d370ae89b8af4d46a45372b269f926ec662d
> > change-id: 20261028-perf-alpha-profileme-8010299be323
> >
> > Best regards,
> > --
> > Matt Turner <mattst88@gmail.com>
> >
> 
> My plan is to take this series through the Alpha tree alongside the
> kernel ProfileMe support. Does that work for the perf maintainers?
> An Acked-by would be appreciated.

Should be ok as it hardly touches the common code.

Acked-by: Namhyung Kim <namhyung@kernel.org>

Ian, does it look ok to you?

Thanks,
Namhyung