From: Dapeng Mi <dapeng1.mi@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Andi Kleen <ak@linux.intel.com>,
Eranian Stephane <eranian@google.com>,
Sandipan Das <sandipan.das@amd.com>,
Andrii Nakryiko <andrii@kernel.org>, Song Liu <song@kernel.org>,
Ravi Bangoria <ravi.bangoria@amd.com>,
Ananth Narayan <ananth.narayan@amd.com>
Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
bpf@vger.kernel.org, Dapeng Mi <dapeng1.mi@intel.com>,
Zide Chen <zide.chen@intel.com>,
Falcon Thomas <thomas.falcon@intel.com>,
Xudong Hao <xudong.hao@intel.com>,
Dapeng Mi <dapeng1.mi@linux.intel.com>
Subject: [Patch v6 14/20] perf/x86/amd: Refresh LBR stack in PMI only when LBR users are active
Date: Fri, 6 Nov 2026 12:32:51 +0800 [thread overview]
Message-ID: <20261106043257.842864-15-dapeng1.mi@linux.intel.com> (raw)
In-Reply-To: <20261106043257.842864-1-dapeng1.mi@linux.intel.com>
Refreshing the LBR stack in the PMI handler is unnecessary when no LBR
users are active. This adds avoidable overhead and hurts performance.
Limit the LBR stack refresh to the PMI path only when LBR users are
present.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Cc: "Sandipan Das <sandipan.das@amd.com>"
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
arch/x86/events/amd/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 160102a46b18..f0425e369837 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -988,7 +988,8 @@ static int amd_pmu_v2_handle_irq(struct pt_regs *regs)
/* Read branch records */
if (x86_pmu.lbr_nr) {
- amd_pmu_lbr_read();
+ if (cpuc->lbr_users > 0)
+ amd_pmu_lbr_read();
status &= ~GLOBAL_STATUS_LBRS_FROZEN;
}
--
2.34.1
next prev parent reply other threads:[~2026-11-06 4:42 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-06 4:32 [Patch v6 00/20] perf/x86: Fix multiple LBR sampling issues Dapeng Mi
2026-11-06 4:32 ` [Patch v6 01/20] perf/x86: Disable LBR if x86_pmu.lbr_nr exceeds MAX_LBR_ENTRIES Dapeng Mi
2026-11-06 4:32 ` [Patch v6 02/20] perf/x86/intel: Validate LBR XSAVE state before updating LBR stack Dapeng Mi
2026-11-06 4:32 ` [Patch v6 03/20] perf/x86/amd/lbr: Limit branch snapshots to valid entries Dapeng Mi
2026-11-06 4:32 ` [Patch v6 04/20] perf/x86/intel/lbr: " Dapeng Mi
2026-11-06 4:32 ` [Patch v6 05/20] perf/x86: Add lbr_enabled to track LBR state Dapeng Mi
2026-11-06 4:32 ` [Patch v6 06/20] perf/x86/amd: Avoid re-enabling PMU and LBR for BPF when disabled Dapeng Mi
2026-11-06 4:32 ` [Patch v6 07/20] perf/x86/intel: Add helper to enable PMU without LBR Dapeng Mi
2026-11-06 4:32 ` [Patch v6 08/20] perf/x86/intel: Avoid re-enabling PMU and LBR for BPF when disabled Dapeng Mi
2026-11-06 4:32 ` [Patch v6 09/20] perf/x86/intel: Keep LBR frozen throughout PMI handling Dapeng Mi
2026-11-06 4:32 ` [Patch v6 10/20] perf: Add counted-bounds tracking for perf_branch_stack Dapeng Mi
2026-11-06 4:32 ` [Patch v6 11/20] perf/x86/intel: Allow LBR read helpers to operate on explicit stacks Dapeng Mi
2026-11-06 4:32 ` [Patch v6 12/20] perf/x86/intel: Use a dedicated LBR stack for BPF snapshotting Dapeng Mi
2026-11-06 4:32 ` [Patch v6 13/20] perf/x86/intel: Always snapshot live hardware LBR state for BPF Dapeng Mi
2026-11-06 4:32 ` Dapeng Mi [this message]
2026-11-06 4:32 ` [Patch v6 15/20] perf/x86/intel: Refresh LBR stack for non-PEBS LBR events when needed Dapeng Mi
2026-11-06 4:32 ` [Patch v6 16/20] perf/x86/intel: Remove dead lbr_pebs_users Dapeng Mi
2026-11-06 4:32 ` [Patch v6 17/20] perf/x86/intel: Clear raw LBR counters in the LBR stack Dapeng Mi
2026-11-06 4:32 ` [Patch v6 18/20] perf/x86/intel: Refill LBR stack for LBR counter events in PMI handler Dapeng Mi
2026-11-06 4:32 ` [Patch v6 19/20] perf/x86/intel: Pass LBR stack size into store_lbr() Dapeng Mi
2026-11-06 4:32 ` [Patch v6 20/20] perf/core: Don't overwrite shared LBR stack depth Dapeng Mi
2026-11-06 7:23 ` [Patch v6 00/20] perf/x86: Fix multiple LBR sampling issues Mi, Dapeng
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