Re: [PATCH v2 1/2] perf jevents: Add IOMMU metrics for AMD

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Fri, May 29, 2026 at 02:56:38PM +0530, Sandipan Das wrote:
> On 29-05-2026 05:14, Chun-Tse Shao wrote:
> > Add IOMMU Translation Lookaside Buffer (TLB) and interrupt cache metrics
> > to perf jevents for AMD platforms. This enhances I/O performance
> > observability, allowing fleet-wide monitoring of IOMMU overhead.
> > 
> > These metrics are supported on Zen 2 and newer processors (Rome, Milan,
> > Genoa, Turin) and are implemented using the standard `amd_iommu` PMU
> > events. The implementation uses the existing `_zen_model` helper to
> > ensure these are only generated for Zen 2+. Note that the pde events on
> > AMD cover both 2M and 1G pages, so 1G pages are implicitly included in
> > the total hits/misses metrics (sum of pte and pde events).
> > 
> > The following metrics are added:
> > - iotlb_total_hit: Total IOTLB hits (4K, 2M, 1G pages).
> > - iotlb_total_miss: Total IOTLB misses.
> > - iotlb_miss_rate: IOTLB miss rate.
> > - iotlb_interrupt_cache_hit: Interrupt cache hits.
> > - iotlb_interrupt_cache_miss: Interrupt cache misses.
> > - iotlb_interrupt_cache_lookup: Interrupt cache lookups.
> > - iotlb_interrupt_cache_miss_rate: Interrupt cache miss rate.
> > 
> > Tested:
> >   # perf stat -M \
> >     iotlb_total_hit,iotlb_total_miss,iotlb_miss_rate \
> >     --per-socket --metric-only -a -j -- sleep 10
> >   {"socket" : "S0", "counters" : 10,
> >    "hits  iotlb_total_hit" : "3579249.0",
> >    "%  iotlb_miss_rate" : "0.0",
> >    "misses  iotlb_total_miss" : "3.0"}
> >   {"socket" : "S1", "counters" : 10,
> >    "hits  iotlb_total_hit" : "0.0",
> >    "%  iotlb_miss_rate" : "0.0",
> >    "misses  iotlb_total_miss" : "0.0"}
> > 
> > Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> > Assisted-by: Gemini:gemini-3.1-pro-preview
> > ---
> 
> Reviewed-by: Sandipan Das <sandipan.das@amd.com>

Thanks, applied both patches and collected Ian's reviewed-by, since he
provided it for the combined patch and requested that it was split,
which this v2 does.

- Arnaldo