Re: [PATCH v6 10/13] alpha/perf: report the data source of ProfileMe memory accesses

[sashiko-bot@kernel.org]

> Whether a ProfileMe sample's memory access missed the DTB is only in the
> PERF_SAMPLE_RAW data, as a DTB miss trap.
> 
> Set PERF_SAMPLE_DATA_SRC for the samples of memory instructions, so that
> the memory sort keys see them. One that trapped on a DTB miss gets an L1
> miss in mem_dtlb. PALcode fills the DTB, so one that retired without
> that trap hit it, and gets an L1 hit. mem_op comes from the opcode, as
> I_STAT does not say whether the access was a load or a store. A load
> into $31 or $f31 is a prefetch, except for ldq_u, a UNOP that is left
> out. Samples that fall back to the interrupted PC get none.
> 
> On an EV7, a loop that loads one word from each page of 64 MB in random
> order had as many DTB hit samples on the load as misses: the miss trap
> aborts the load, and its refetch hits. A prefetch into $31 takes the
> same trap, and its samples are reported as PFETCH misses and hits.
> 
> I_STAT[TRP] is ignored for an instruction killed before it was mapped. On
> an EV7, TRP and MIS were seen set for killed instructions that are not
> even branches.
> 
> Suggested-by: Ian Rogers <irogers@google.com>
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261104-alpha-profileme-v6-0-63362e9290a3@gmail.com?part=10