Re: [PATCH V9 10/10] arm64/perf: Implement branch records save on PMU IRQ
From: James Clark <hidden>
Date: 2023-05-23 14:39:11
Also in:
linux-perf-users, lkml
On 15/03/2023 05:14, Anshuman Khandual wrote:
This modifies armv8pmu_branch_read() to concatenate live entries along with task context stored entries and then process the resultant buffer to create perf branch entry array for perf_sample_data. It follows the same principle like task sched out. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual <redacted> ---
[...]
quoted hunk ↗ jump to hunk
void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event) { struct brbe_hw_attr *brbe_attr = (struct brbe_hw_attr *)cpuc->percpu_pmu->private; + struct arm64_perf_task_context *task_ctx = event->pmu_ctx->task_ctx_data; + struct brbe_regset live[BRBE_MAX_ENTRIES]; + int nr_live, nr_store; u64 brbfcr, brbcr; - int idx, loop1_idx1, loop1_idx2, loop2_idx1, loop2_idx2, count; brbcr = read_sysreg_s(SYS_BRBCR_EL1); brbfcr = read_sysreg_s(SYS_BRBFCR_EL1);@@ -739,36 +743,13 @@ void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event) write_sysreg_s(brbfcr | BRBFCR_EL1_PAUSED, SYS_BRBFCR_EL1); isb(); - /* Determine the indices for each loop */ - loop1_idx1 = BRBE_BANK0_IDX_MIN; - if (brbe_attr->brbe_nr <= BRBE_BANK_MAX_ENTRIES) { - loop1_idx2 = brbe_attr->brbe_nr - 1; - loop2_idx1 = BRBE_BANK1_IDX_MIN; - loop2_idx2 = BRBE_BANK0_IDX_MAX; - } else { - loop1_idx2 = BRBE_BANK0_IDX_MAX; - loop2_idx1 = BRBE_BANK1_IDX_MIN; - loop2_idx2 = brbe_attr->brbe_nr - 1; - } - - /* Loop through bank 0 */ - select_brbe_bank(BRBE_BANK_IDX_0); - for (idx = 0, count = loop1_idx1; count <= loop1_idx2; idx++, count++) { - if (!capture_branch_entry(cpuc, event, idx)) - goto skip_bank_1; - } - - /* Loop through bank 1 */ - select_brbe_bank(BRBE_BANK_IDX_1); - for (count = loop2_idx1; count <= loop2_idx2; idx++, count++) { - if (!capture_branch_entry(cpuc, event, idx)) - break; - } - -skip_bank_1: - cpuc->branches->branch_stack.nr = idx; - cpuc->branches->branch_stack.hw_idx = -1ULL; + nr_live = capture_brbe_regset(brbe_attr, live); + nr_store = task_ctx->nr_brbe_records; + nr_store = stitch_stored_live_entries(task_ctx->store, live, nr_store, + nr_live, brbe_attr->brbe_nr); + process_branch_entries(cpuc, event, task_ctx->store, nr_store);
Hi Anshuman, With the following command I get a crash: perf record --branch-filter any,save_type -a -- ls [ 101.171822] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000600 ... [145380.414654] Call trace: [145380.414739] armv8pmu_branch_read+0x7c/0x578 [145380.414895] armv8pmu_handle_irq+0x104/0x1c0 [145380.415043] armpmu_dispatch_irq+0x38/0x70 [145380.415209] __handle_irq_event_percpu+0x124/0x3b8 [145380.415392] handle_irq_event+0x54/0xc8 [145380.415567] handle_fasteoi_irq+0x100/0x1e0 [145380.415718] generic_handle_domain_irq+0x38/0x58 [145380.415895] gic_handle_irq+0x5c/0x130 [145380.416025] call_on_irq_stack+0x24/0x58 [145380.416173] el1_interrupt+0x74/0xc0 [145380.416321] el1h_64_irq_handler+0x18/0x28 [145380.416475] el1h_64_irq+0x64/0x68 [145380.416604] smp_call_function_single+0xe8/0x1f0 [145380.416745] event_function_call+0xbc/0x1c8 [145380.416919] _perf_event_enable+0x84/0xa0 [145380.417069] perf_ioctl+0xe8/0xd68 [145380.417204] __arm64_sys_ioctl+0x9c/0xe0 [145380.417353] invoke_syscall+0x4c/0x120 [145380.417523] el0_svc_common+0xd0/0x120 [145380.417693] do_el0_svc+0x3c/0xb8 [145380.417859] el0_svc+0x50/0xc0 [145380.418004] el0t_64_sync_handler+0x84/0xf0 [145380.418160] el0t_64_sync+0x190/0x198 When using --branch-filter any,u without -a it seems to be fine so could be that task_ctx is null in per-cpu mode, or something to do with the userspace only flag? I'm also wondering if it's possible to collapse some of the last 5 commits? They seem to mostly modify things in brbe.c which is a new file so the history probably isn't important at this point it just makes it a bit harder to review.
process_branch_aborts(cpuc); + task_ctx->nr_brbe_records = 0; /* Unpause the buffer */ write_sysreg_s(brbfcr & ~BRBFCR_EL1_PAUSED, SYS_BRBFCR_EL1);
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