Messages in this thread | | | From | Tianyi Liu <> | Subject | [PATCH v2 0/5] perf: KVM: Enable callchains for guests | Date | Sun, 8 Oct 2023 22:48:17 +0800 |
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Hi there,
This series of patches enables callchains for guests (used by perf kvm), which holds the top spot on the perf wiki TODO list [1]. This allows users to perform guest OS callchain or performance analysis from external using PMU events.
The event processing flow is as follows (shown as backtrace): #0 kvm_arch_vcpu_get_frame_pointer / kvm_arch_vcpu_read_virt (per arch) #1 kvm_guest_get_frame_pointer / kvm_guest_read_virt <callback function pointers in `struct perf_guest_info_callbacks`> #2 perf_guest_get_frame_pointer / perf_guest_read_virt #3 perf_callchain_guest #4 get_perf_callchain #5 perf_callchain
Between #0 and #1 is the interface between KVM and the arch-specific impl, while between #1 and #2 is the interface between Perf and KVM. The 1st patch implements #0. The 2nd patch extends interfaces between #1 and #2, while the 3rd patch implements #1. The 4th patch implements #3 and modifies #4 #5. The last patch is for userspace utils.
Since arm64 hasn't provided some foundational infrastructure (interface for reading from a virtual address of guest), the arm64 implementation is stubbed for now because it's a bit complex, and will be implemented later.
Tested with both 32-bit and 64-bit guest operating systems / unikernels, that `perf script` could correctly show the certain callchains. FlameGraphs can also be generated with this series of patches and [2].
Any feedback will be greatly appreciated.
[1] https://perf.wiki.kernel.org/index.php/Todo [2] https://github.com/brendangregg/FlameGraph
v1: https://lore.kernel.org/kvm/SYYP282MB108686A73C0F896D90D246569DE5A@SYYP282MB1086.AUSP282.PROD.OUTLOOK.COM/
Changes since v1: - v1 only includes partial KVM modifications, while v2 is a complete implementation. Also updated based on Sean's feedback.
Tianyi Liu (5): KVM: Add arch specific interfaces for sampling guest callchains perf kvm: Introduce guest interfaces for sampling callchains KVM: implement new perf interfaces perf kvm: Support sampling guest callchains perf tools: Support PERF_CONTEXT_GUEST_* flags
arch/arm64/kvm/arm.c | 17 +++++++++ arch/x86/events/core.c | 56 +++++++++++++++++++++++------ arch/x86/kvm/x86.c | 18 ++++++++++ include/linux/kvm_host.h | 4 +++ include/linux/perf_event.h | 18 +++++++++- kernel/bpf/stackmap.c | 8 ++--- kernel/events/callchain.c | 27 +++++++++++++- kernel/events/core.c | 17 ++++++++- tools/perf/builtin-timechart.c | 6 ++++ tools/perf/util/data-convert-json.c | 6 ++++ tools/perf/util/machine.c | 6 ++++ virt/kvm/kvm_main.c | 25 +++++++++++++ 12 files changed, 191 insertions(+), 17 deletions(-)
base-commit: 8a749fd1a8720d4619c91c8b6e7528c0a355c0aa -- 2.42.0
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