From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=192.198.163.10 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794477580; b=44dGXDc5J6jBmIJkqTHuC3QfYe7kR7FglRqLRXVL136tMZCFdgVujIvNOXT0cDnv0j1P htFGVaKxbPxrw1NGNTOJT3gLvsLQKUMf9l6XoUdoXnUDL3rhdfRf5oROdNGtV3SjsRdZt G+pHmNAW97+JAmUhJZn1Ia6GiKhehBtFeNr7QUfPntsTehmw3yiXP47t3Ikjq6Xu6H/Y2 6K/55jMcB99ILAz25cfOPtwhRoE38OIschnSakP0QS0T8TYln7AWUrqh2WWAGepgCdsim s8NVmwTwjkXu2IcLyu2L888bYVmIEd1iWh4E6vaw9QKDo6Hp1yd04yzTO0wuDXpD5Tw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794477580; h=DMARC-Filter:DKIM-Signature:X-CSE-ConnectionGUID:X-CSE-MsgGUID: X-IronPort-AV:X-IronPort-AV:Received:X-CSE-ConnectionGUID: X-CSE-MsgGUID:X-ExtLoop1:X-IronPort-AV:Received:Message-ID:Date: MIME-Version:User-Agent:Subject:To:Cc:References:Content-Language: From:In-Reply-To:Content-Type:Content-Transfer-Encoding; bh=2E/Pd+eRpGBVsTZHlPb0fwZaxBzjHwZ9HH30lAHAHJQ=; b=jInO8dAxNW+7EoyovU4h7qEfU/s1aegwmCxAqyQjgoex28r1lKtgLHuX849LzZNi8ie3 qiLoGB2CSQy1WhwcUGbpdQZzO1jhRqrznQs7Vx9/I33vY6EuLfJcItnzmebBw1OkenDDQ oCNPeus2CmR17qcz/Z8CXlo5j3FRSLNPbwlZRJLBqtX73VD5lHWy9I0uh7ofcVSoWMGDP CI1SuiE0NMEcZIW/XT/OHAQ5624VeBD7rp6wcPPDw/E8IIzHCQlKGJvIqrwbPE5uVyiLI OO7R3pGsuZsnCvscHihP+lZABWJt8EFYwOYgkWN07YWsga5FvnCoq1/o70ZS+MBZFBQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=XGGiy1bp; arc=none smtp.remote-ip=192.198.163.10 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.10]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C273F606A31C; Thu, 12 Nov 2026 09:59:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org C273F606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=XGGiy1bp DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1794477579; x=1826013579; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=qDule4CxqfFN+2waxds8SOiRRp9p+9tYIgVSLDGdBfo=; b=XGGiy1bp26JXi74cBmiQNum0JK5EbTJCO/FvsAIQC3xysw16wqFTNClk FMi0a0DTbCHVFoLZPXPSKhRYaHL3voRQQv//736Q28Sm/74F1q4qwNeQa NoZ47FHHjG6ad6wQnrVC/ltWuOlzYF2Pnxv5axvrspqC/JZgKrb1UnIfv EujeQDTFeU78wBYHsWU4ffyuwR0OYxfsyVCcvd9USrV0vqjV6MjvzibpU PKETtRFoB2yRDWrBwvrc/zaXJKV0cnpCPcFZwS0tKrnGm/xC4fOxh7Dpe 9sNkXbzDeoUPuHtROVxjoQESmRoRNaHD9Pi71V3a0uW0W8S0cY8932zGx w==; X-CSE-ConnectionGUID: D2a60SZGSgys/4InDmVj9w== X-CSE-MsgGUID: xYM5J97VQNybr/Yf+r+9vA== X-IronPort-AV: E=McAfee;i="6800,10657,11963"; a="3157926" X-IronPort-AV: E=Sophos;i="6.27,209,1787036400"; d="scan'208";a="3157926" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2026 01:59:39 -0800 X-CSE-ConnectionGUID: kd8jmuNnQ16CVZxt1cNRrg== X-CSE-MsgGUID: bjpelCUYTvOrAS89RdBqiA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,209,1787036400"; d="scan'208";a="8445167" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.241.239]) ([10.124.241.239]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2026 01:59:34 -0800 Message-ID: <9464097b-a8e0-47d8-aa63-d56af1d30c84@linux.intel.com> Date: Thu, 12 Nov 2026 17:59:30 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Patch v6 14/20] perf/x86/amd: Refresh LBR stack in PMI only when LBR users are active To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Ian Rogers , Adrian Hunter , Alexander Shishkin , Andi Kleen , Eranian Stephane , Sandipan Das , Andrii Nakryiko , Song Liu , Ravi Bangoria , Ananth Narayan Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, bpf@vger.kernel.org, Dapeng Mi , Zide Chen , Falcon Thomas , Xudong Hao References: <20261106043257.842864-1-dapeng1.mi@linux.intel.com> <20261106043257.842864-15-dapeng1.mi@linux.intel.com> Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: <20261106043257.842864-15-dapeng1.mi@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/6/2026 12:32 PM, Dapeng Mi wrote: > 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 > Cc: "Sandipan Das " > Signed-off-by: Dapeng Mi > --- > 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; > } > This patch is actually unnecessary since amd_pmu_lbr_read() internally checks cpuc->lbr_users and would early return if cpuc->lbr_users is 0.  Would drop this patch in next version. Thanks.