From: Hang Zhengyang <hang.zhengyang1010@gmail.com>
To: Jacob Lefkowitz <jlefkowi@akamai.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
James Clark <james.clark@linaro.org>,
Ravi Bangoria <ravi.bangoria@amd.com>,
Ben Chaney <bchaney@akamai.com>,
Matt Pelland <mpelland@akamai.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/2] perf jevents: Add IOMMU PTW & device entry metrics
Date: Tue, 10 Nov 2026 11:22:30 +0800 [thread overview]
Message-ID: <20261110032232.3080268-1-hang.zhengyang1010@gmail.com> (raw)
In-Reply-To: <20261102-perf-tools-next-v2-0-4d237f886710@akamai.com>
On Mon, 02 Nov 2026 21:14:15 +0000, Jacob Lefkowitz wrote:
> Adds AMD specific metrics for the IOMMU with respect to page table
> walks and device table entires.
Tested on Zen 3 (Ryzen 7 PRO 5850U) on top of perf-tools-next
13a8d580433a. Both groups show up and count, perf test 130 and 131
pass, and under O_DIRECT reads from NVMe the values match the raw
amd_iommu_0 counts.
Tested-by: Hang Zhengyang <hang.zhengyang1010@gmail.com>
Two values look odd on this machine:
- lpm_iommu_ptw_nested_read_ratio is 100% with no guest running:
page_tbl_read_nst equals page_tbl_read_tot.
- lpm_iommu_ptw_reads_per_tlb_miss is about 0.2: 142588 page table
reads against 440805 pte and 192018 pde misses.
Ravi, are these expected on Zen 3?
(Tested with the help of an AI assistant; I checked the results.)
prev parent reply other threads:[~2026-11-10 3:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-02 21:14 Jacob Lefkowitz via B4 Relay
2026-11-02 21:14 ` [PATCH v2 1/2] perf jevents: add iommu page table walk metrics Jacob Lefkowitz via B4 Relay
2026-11-02 21:14 ` [PATCH v2 2/2] perf jevents: add amd specific device table entry metrics Jacob Lefkowitz via B4 Relay
2026-11-10 3:22 ` Hang Zhengyang [this message]
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