Re: [PATCH] perf: riscv: skip empty batches in counter start
From: Anup Patel <anup@brainfault.org>
Date: 2025-08-04 04:54:40
Also in:
linux-perf-users, linux-riscv, lkml
On Mon, Aug 4, 2025 at 8:21 AM Yunhui Cui [off-list ref] wrote:
Avoid unnecessary SBI calls when starting non-overflowed counters in pmu_sbi_start_ovf_ctrs_sbi() by checking ctr_start_mask. Signed-off-by: Yunhui Cui <redacted>
LGTM. Reviewed-by: Anup Patel <anup@brainfault.org> Regards, Anup
quoted hunk ↗ jump to hunk
--- drivers/perf/riscv_pmu_sbi.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c index 698de8ddf895b..3977f7488e4ef 100644 --- a/drivers/perf/riscv_pmu_sbi.c +++ b/drivers/perf/riscv_pmu_sbi.c@@ -877,8 +877,10 @@ static inline void pmu_sbi_start_ovf_ctrs_sbi(struct cpu_hw_events *cpu_hw_evt, for (i = 0; i < BITS_TO_LONGS(RISCV_MAX_COUNTERS); i++) { ctr_start_mask = cpu_hw_evt->used_hw_ctrs[i] & ~ctr_ovf_mask; /* Start all the counters that did not overflow in a single shot */ - sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_START, i * BITS_PER_LONG, ctr_start_mask, - 0, 0, 0, 0); + if (ctr_start_mask) { + sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_COUNTER_START, i * BITS_PER_LONG, + ctr_start_mask, 0, 0, 0, 0); + } } /* Reinitialize and start all the counter that overflowed */ --2.39.5