[PATCH v2 0/2] riscv: Add perf support to collect KVM guest statistics from host side

zhouquan
2024-08-13T13:23:55Z

From: Quan Zhou <zhouquan@iscas.ac.cn>

Add basic guest support to RISC-V perf, enabling it to distinguish
whether PMU interrupts occur in the host or the guest, and then
collect some basic guest information from the host side
(guest os callchain is not supported for now).

Based on the x86/arm implementation, tested with kvm-riscv.
test env:
- host: qemu-9.0.0
- guest: qemu-9.0.0 --enable-kvm (only start one guest and run top)

-----------------------------------------
1) perf kvm top
./perf kvm --host --guest \
--guestkallsyms=/root/repo/shared/kallsyms \
--guestmodules=/root/repo/shared/modules top

PerfTop: 41 irqs/sec kernel:97.6% us: 0.0% guest kernel: 0.0% guest us: 0.0% exact: 0.0% [250Hz cycles:P], (all, 4 CPUs)
-------------------------------------------------------------------------------

64.57% [kernel] [k] default_idle_call
3.12% [kernel] [k] _raw_spin_unlock_irqrestore
3.03% [guest.kernel] [g] mem_serial_out
2.61% [kernel] [k] handle_softirqs
2.32% [kernel] [k] do_trap_ecall_u
1.71% [kernel] [k] _raw_spin_unlock_irq
1.26% [guest.kernel] [g] do_raw_spin_lock
1.25% [kernel] [k] finish_task_switch.isra.0
1.16% [kernel] [k] do_idle
0.77% libc.so.6 [.] ioctl
0.76% [kernel] [k] queue_work_on
0.69% [kernel] [k] __local_bh_enable_ip
0.67% [guest.kernel] [g] __noinstr_text_start
0.64% [guest.kernel] [g] mem_serial_in
0.41% libc.so.6 [.] pthread_sigmask
0.39% [kernel] [k] mem_cgroup_uncharge_skmem
0.39% [kernel] [k] __might_resched
0.39% [guest.kernel] [g] _nohz_idle_balance.isra.0
0.37% [kernel] [k] sched_balance_update_blocked_averages
0.34% [kernel] [k] sched_balance_rq

2) perf kvm record
./perf kvm --host --guest \
--guestkallsyms=/root/repo/shared/kallsyms \
--guestmodules=/root/repo/shared/modules record -a sleep 60

[ perf record: Woken up 3 times to write data ]
[ perf record: Captured and wrote 1.292 MB perf.data.kvm (17990 samples) ]

3) perf kvm report (the data shown here is not complete)
./perf kvm --host --guest \
--guestkallsyms=/root/repo/shared/kallsyms \
--guestmodules=/root/repo/shared/modules report -i perf.data.kvm

# Total Lost Samples: 0
#
# Samples: 17K of event 'cycles:P'
# Event count (approx.): 269968947184
#
# Overhead Command Shared Object Symbol
# ........ ............... ....................... ..............................................
#
61.86% swapper [kernel.kallsyms] [k] default_idle_call
2.93% :6463 [guest.kernel.kallsyms] [g] do_raw_spin_lock
2.82% :6462 [guest.kernel.kallsyms] [g] mem_serial_out
2.11% sshd [kernel.kallsyms] [k] _raw_spin_unlock_irqrestore
1.78% :6462 [guest.kernel.kallsyms] [g] do_raw_spin_lock
1.37% swapper [kernel.kallsyms] [k] handle_softirqs
1.36% swapper [kernel.kallsyms] [k] do_idle
1.21% sshd [kernel.kallsyms] [k] do_trap_ecall_u
1.21% sshd [kernel.kallsyms] [k] _raw_spin_unlock_irq
1.11% qemu-system-ris [kernel.kallsyms] [k] do_trap_ecall_u
0.93% qemu-system-ris libc.so.6 [.] ioctl
0.89% sshd [kernel.kallsyms] [k] __local_bh_enable_ip
0.77% qemu-system-ris [kernel.kallsyms] [k] _raw_spin_unlock_irqrestore
0.68% qemu-system-ris [kernel.kallsyms] [k] queue_work_on
0.65% sshd [kernel.kallsyms] [k] handle_softirqs
0.44% :6462 [guest.kernel.kallsyms] [g] mem_serial_in
0.42% sshd libc.so.6 [.] pthread_sigmask
0.34% :6462 [guest.kernel.kallsyms] [g] serial8250_tx_chars
0.30% swapper [kernel.kallsyms] [k] finish_task_switch.isra.0
0.29% swapper [kernel.kallsyms] [k] sched_balance_rq
0.29% sshd [kernel.kallsyms] [k] __might_resched
0.26% swapper [kernel.kallsyms] [k] tick_nohz_idle_exit
0.26% swapper [kernel.kallsyms] [k] sched_balance_update_blocked_averages
0.26% swapper [kernel.kallsyms] [k] _nohz_idle_balance.isra.0
0.24% qemu-system-ris [kernel.kallsyms] [k] finish_task_switch.isra.0
0.23% :6462 [guest.kernel.kallsyms] [g] __noinstr_text_start

---
Change since v1:
- Rebased on v6.11-rc3
- Fix incorrect misc type (Andrew)

---
v1 link:
https://lore.kernel.org/all/cover.1721271251.git.zhouquan@iscas.ac.cn/

Quan Zhou (2):
riscv: perf: add guest vs host distinction
riscv: KVM: add basic support for host vs guest profiling

arch/riscv/include/asm/kvm_host.h | 5 ++++
arch/riscv/include/asm/perf_event.h | 7 ++++++
arch/riscv/kernel/perf_callchain.c | 38 +++++++++++++++++++++++++++++
arch/riscv/kvm/Kconfig | 1 +
arch/riscv/kvm/main.c | 12 +++++++--
arch/riscv/kvm/vcpu.c | 7 ++++++
6 files changed, 68 insertions(+), 2 deletions(-)

base-commit: 7c626ce4bae1ac14f60076d00eafe71af30450ba
--
2.34.1