linux-kernel - Re: [PATCH v2 0/2] perf kvm: Add kvm stat support on riscv

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Message-ID: <aceaaeba-61cb-44fa-8639-e30a86ef8cd8@rivosinc.com>
Date: Tue, 16 Apr 2024 17:25:06 -0700
From: Atish Patra <atishp@...osinc.com>
To: Shenlin Liang <liangshenlin@...incomputing.com>, anup@...infault.org,
 atishp@...shpatra.org, paul.walmsley@...ive.com, palmer@...belt.com,
 aou@...s.berkeley.edu, kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
 namhyung@...nel.org, mark.rutland@....com,
 alexander.shishkin@...ux.intel.com, jolsa@...nel.org, irogers@...gle.com,
 adrian.hunter@...el.com, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 0/2] perf kvm: Add kvm stat support on riscv

On 4/14/24 20:11, Shenlin Liang wrote:
> Changes from v1->v2:
> - Rebased on Linux 6.9-rc3.
> 
> 'perf kvm stat report/record' generates a statistical analysis of KVM
> events and can be used to analyze guest exit reasons. This patch tries
> to add stat support on riscv.
> 
> Map the return value of trace_kvm_exit() to the specific cause of the
> exception, and export it to userspace.
> 
> It records on two available KVM tracepoints for riscv: "kvm:kvm_entry"
> and "kvm:kvm_exit", and reports statistical data which includes events
> handles time, samples, and so on.
> 
> Simple tests go below:
> 
> # ./perf kvm record -e "kvm:kvm_entry" -e "kvm:kvm_exit"
> Lowering default frequency rate from 4000 to 2500.
> Please consider tweaking /proc/sys/kernel/perf_event_max_sample_rate.
> [ perf record: Woken up 18 times to write data ]
> [ perf record: Captured and wrote 5.433 MB perf.data.guest (62519 samples)
> 

I want to test these patches but couldn't build a perf for RISC-V with 
libtraceevent enabled. It fails with pkg-config dependencies when I 
tried to build it (both via buildroot and directly from kernel source).

> # ./perf kvm report
> 31K kvm:kvm_entry
> 31K kvm:kvm_exit
> 
> # ./perf kvm stat record -a
> [ perf record: Woken up 3 times to write data ]
> [ perf record: Captured and wrote 8.502 MB perf.data.guest (99338 samples) ]
> 
> # ./perf kvm stat report --event=vmexit
> Event name                Samples   Sample%    Time (ns)     Time%   Max Time (ns)   Min Time (ns)  Mean Time (ns)
> STORE_GUEST_PAGE_FAULT     26968     54.00%    2003031800    40.00%     3361400         27600          74274
> LOAD_GUEST_PAGE_FAULT      17645     35.00%    1153338100    23.00%     2513400         30800          65363
> VIRTUAL_INST_FAULT         1247      2.00%     340820800     6.00%      1190800         43300          273312
> INST_GUEST_PAGE_FAULT      1128      2.00%     340645800     6.00%      2123200         30200          301990
> SUPERVISOR_SYSCALL         1019      2.00%     245989900     4.00%      1851500         29300          241403
> LOAD_ACCESS                986       1.00%     671556200     13.00%     4180200         100700         681091
> INST_ACCESS                655       1.00%     170054800     3.00%      1808300         54600          259625
> HYPERVISOR_SYSCALL         21        0.00%     4276400       0.00%      716500          116000         203638
> 
> Shenlin Liang (2):
>    RISCV: KVM: add tracepoints for entry and exit events
>    perf kvm/riscv: Port perf kvm stat to RISC-V
> 
>   arch/riscv/kvm/trace.h                        | 67 ++++++++++++++++
>   arch/riscv/kvm/vcpu.c                         |  7 ++
>   tools/perf/arch/riscv/Makefile                |  1 +
>   tools/perf/arch/riscv/util/Build              |  1 +
>   tools/perf/arch/riscv/util/kvm-stat.c         | 78 +++++++++++++++++++
>   .../arch/riscv/util/riscv_exception_types.h   | 41 ++++++++++
>   6 files changed, 195 insertions(+)
>   create mode 100644 arch/riscv/kvm/trace.h
>   create mode 100644 tools/perf/arch/riscv/util/kvm-stat.c
>   create mode 100644 tools/perf/arch/riscv/util/riscv_exception_types.h
>