| Message ID | 20200924110706.254996-1-alexandru.elisei@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | arm_pmu: Use NMI for perf interrupt | expand |
On Thu, 24 Sep 2020 12:06:59 +0100, Alexandru Elisei wrote: > The series changes the arm_pmu driver to use NMIs for the perf interrupt > when NMIs are available on the platform (currently, only arm64 + GICv3). To > make it easier to play with the patches, I've pushed a branch at [1]: > > $ git clone -b pmu-nmi-v7 git://linux-arm.org/linux-ae > > The changes from v6 were minor, but I've still run the same tests on an > espressobin v7*. These are the results of running perf record -a -- sleep > 60 (all results show kernel symbols with overhead >= 1%): > > [...] Applied to will (for-next/perf), thanks! [1/7] arm64: perf: Add missing ISB in armv8pmu_enable_counter() https://git.kernel.org/will/c/490d7b7c0845 [2/7] arm64: perf: Avoid PMXEV* indirection https://git.kernel.org/will/c/0fdf1bb75953 [3/7] arm64: perf: Remove PMU locking https://git.kernel.org/will/c/2a0e2a02e4b7 [4/7] arm64: perf: Defer irq_work to IPI_IRQ_WORK https://git.kernel.org/will/c/05ab72813340 [5/7] KVM: arm64: pmu: Make overflow handler NMI safe https://git.kernel.org/will/c/95e92e45a454 [6/7] arm_pmu: Introduce pmu_irq_ops https://git.kernel.org/will/c/f76b130bdb89 [7/7] arm_pmu: arm64: Use NMIs for PMU https://git.kernel.org/will/c/d8f6267f7ce5 Cheers,
The series changes the arm_pmu driver to use NMIs for the perf interrupt when NMIs are available on the platform (currently, only arm64 + GICv3). To make it easier to play with the patches, I've pushed a branch at [1]: $ git clone -b pmu-nmi-v7 git://linux-arm.org/linux-ae The changes from v6 were minor, but I've still run the same tests on an espressobin v7*. These are the results of running perf record -a -- sleep 60 (all results show kernel symbols with overhead >= 1%): 1. Without the patches: 11.14% [k] _raw_spin_unlock_irq 9.09% [k] _raw_spin_unlock_irqrestore 8.55% [k] arch_cpu_idle 2.60% [k] __softirqentry_text_start 1.13% [k] arch_counter_get_cntpct 1.13% [k] tick_nohz_idle_exit 1.09% [k] el0_svc_common.constprop.0 [..] 2. Using NMIs: 9.46% [k] arch_counter_get_cntpct 5.59% [k] wait_for_xmitr 3.78% [k] ktime_get 3.63% [k] __delay 1.54% [k] _raw_write_lock_irqsave 1.29% [k] arch_timer_evtstrm_available 1.24% [k] _raw_spin_lock_irqsave 1.11% [k] refresh_cpu_vm_stats 1.06% [k] __schedule 1.03% [k] _find_next_bit.constprop.0 [..] When running perf record -a -- iperf3 -c 127.0.0.1 -t 60: 1. Without the patches: 25.46% [k] __arch_copy_from_user 24.06% [k] __arch_copy_to_user 4.17% [k] _raw_spin_unlock_irq 2.52% [k] _raw_spin_unlock_irqrestore 1.90% [k] __free_pages_ok 1.22% [k] get_page_from_freelist 1.21% [k] arch_cpu_idle 1.19% [k] tcp_ack [..] 2. Using NMIs: 23.94% [k] __arch_copy_from_user 21.65% [k] __arch_copy_to_user 1.19% [k] tcp_ack [..] I've run the same tests in a VM when both host+guest use NMIs, and when they don't. All of these tests were also ran on the model. Similar results in all cases. * All the firmware versions for espressobin v7 that I've tried clear SCR_EL3.FIQ, which means that NMIs don't work with the upstream kernel. To test the series, I've applied the patches from irq/irqchip-next to enable pseudo-NMIs when SCR_EL3.FIQ == 0. I've also pushed a branch [2] with the patches applied on top of this series: $ git clone -b pmu-nmi-v7-nmi-fiq-clear-v3 git://linux-arm.org/linux-ae Summary of the patches: * Patch 1 is a fix for a bug that Julien found during the review for v4. * Patches 2 and 3 remove locking from arm64 perf event code. * Patches 4 and 5 makes the arm64 PMU interrupt handler NMI safe. * Patches 6 and 7 enable the use of NMIs on arm64 with a GICv3 irqchip. Changes since v6 [3]: - Rebased on top of v5.9-rc6 - Moved the ISBs to armv8pmu_{enable, disable}_counter() - Added irq_work_sync() to kvm_pmu_vcpu_destroy() - Reworked armpmu_find_irq_ops() as per Will's suggestion - Print message when NMIs are used by the PMU - The changes were minor, so I've added the Tested-by tag for v6 from Sumit Garg. Many thanks for the testing! Changes since v5 [4]: - Rebased on top of v5.9-rc1. - Typo fixes. - Added comments to the ISB added by patches #1 and #2. - Reworded message for patch #4, as per Mark's excellent suggestion. Changes since v4 [5]: - Rebased on top of v5.8-rc1 and dropped the Tested-by tags because it's been almost a year since the series has been tested. - Dropped patch 3 because I couldn't find any instance where armv7pmu_read_counter() was called with interrupts enabled. I've also tested this by running several instances of perf for a few hours, and the function was called every time with interrupts disabled. - Dropped patches 4 and 5 because the tradeoff wasn't worth it in my opinion: the irq handler was slower all the time (because it saved/restored the counter select register), in exchange for being slightly faster on the rare ocassions when it triggered at the beginning of the critical sections. - Minor changes here and there to address review comments. Changes since v3 [6]: - Added tags - Fix build issue for perf_event_v6 - Don't disable preemption in pmu->enable() - Always rely on IPI_IRQ_WORK to run the queued work - Fixed typos + cleanups Changes since v2 [7]: - Rebased on recent linux-next (next-20190708) - Fixed a number of bugs with indices (reported by Wei) - Minor style fixes Changes since v1 [8]: - Rebased on v5.1-rc1 - Pseudo-NMI has changed a lot since then, use the (now merged) NMI API - Remove locking from armv7 perf_event - Use locking only in armv6 perf_event - Use direct counter/type registers insted of selector register for armv8 [1] http://www.linux-arm.org/git?p=linux-ae.git;a=shortlog;h=refs/heads/pmu-nmi-v7 [2] http://www.linux-arm.org/git?p=linux-ae.git;a=shortlog;h=refs/heads/pmu-nmi-v7-nmi-fiq-clear-v3 [3] https://lkml.org/lkml/2020/8/19/671 [4] https://www.spinics.net/lists/kernel/msg3554236.html [5] https://lists.infradead.org/pipermail/linux-arm-kernel/2019-July/666824.html [6] https://lists.infradead.org/pipermail/linux-arm-kernel/2019-July/665339.html [7] https://lists.infradead.org/pipermail/linux-arm-kernel/2019-March/640536.html [8] https://lists.infradead.org/pipermail/linux-arm-kernel/2018-January/554611.html Alexandru Elisei (1): arm64: perf: Add missing ISB in armv8pmu_enable_counter() Julien Thierry (5): arm64: perf: Remove PMU locking arm64: perf: Defer irq_work to IPI_IRQ_WORK KVM: arm64: pmu: Make overflow handler NMI safe arm_pmu: Introduce pmu_irq_ops arm_pmu: arm64: Use NMIs for PMU Mark Rutland (1): arm64: perf: Avoid PMXEV* indirection arch/arm64/kernel/perf_event.c | 146 ++++++++++++++++++++----------- arch/arm64/kvm/pmu-emul.c | 26 +++++- drivers/perf/arm_pmu.c | 155 ++++++++++++++++++++++++++++----- include/kvm/arm_pmu.h | 1 + 4 files changed, 255 insertions(+), 73 deletions(-)