From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7E68B2750E6; Tue, 16 Dec 2025 06:59:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765868397; cv=none; b=SaCdpZUM5hVDiGkkUBhaujVhCp891uHZYTvibZQ/34WJwMLHPaBA7SCvnKH7VK9O/ZYZ6CRlCX2LSHhwI0mw17s6SavqX2sj/hosrstgtR2Qs/IphVscd5e5LfbZyZ49xDU+vXyuakdks5SIeLacpW911BwungEffVGILH5/EP8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765868397; c=relaxed/simple; bh=wjW212gumh3kw5PzOaX7J4zfFsANyVYVsOLFjjyO3oA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=dlrcxLJ3AknM/H0h4w195f3usFOz/tVvEZSm1Tj1lolSshTVNv6l6Jdv89njZAfjN2bdPcL8bLc+nfAygtedoS5eEDRRCOhAISDcMLWUAEY2/dU5Rt7F78Z+u3AbzBxeAdshnUShu2HmIiPLBbqT8IyemuydayEj+MC88zKjcOs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=esyXfgyf; arc=none smtp.client-ip=198.175.65.18 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) header.d=intel.com header.i=@intel.com header.b="esyXfgyf" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1765868395; x=1797404395; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=wjW212gumh3kw5PzOaX7J4zfFsANyVYVsOLFjjyO3oA=; b=esyXfgyfHIk2jpdlrJ+hg7Hp3dR59qDzA5hviD90XhW/P/wHHi7pRm9M Zoy7uponjFDZ86XKl+JaHMyqw1GuZl5y4GvbeLUR2NAK592zh+wS+6/11 r7UAi5IPHkncj/jjlccUvmD2o+Avlf5LJP1RlgaWJZEd2X6mXoUSjFqpf 8hoBQ/HDL4UD/h7tP7E79kmlTuv5hH7TbBw4RsQn5LRUjfZKuD6CaFE59 KEJrsSzSxkxFih1ziikWiHFFRKtK+41JC/JtXzfnhCiTWwgf9JL9ksurb nqpfcwZfGSV3ClprWPPmjF/cU8O9j9Hyxdu0mR+Xz/6h5k98Sjwsaa5Xt w==; X-CSE-ConnectionGUID: Aj9EhpvvSxS2ksOOrc1pkg== X-CSE-MsgGUID: vFS+NACeR/iL7Qm3x19iMA== X-IronPort-AV: E=McAfee;i="6800,10657,11643"; a="67814179" X-IronPort-AV: E=Sophos;i="6.21,152,1763452800"; d="scan'208";a="67814179" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by orvoesa110.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Dec 2025 22:59:54 -0800 X-CSE-ConnectionGUID: 6d5jH5UXS9GvwjL1QNA58w== X-CSE-MsgGUID: 99wM7a+3RpWhvhhOwVnMTw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,152,1763452800"; d="scan'208";a="203043615" Received: from dapengmi-mobl1.ccr.corp.intel.com (HELO [10.124.240.14]) ([10.124.240.14]) by orviesa005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Dec 2025 22:59:49 -0800 Message-ID: Date: Tue, 16 Dec 2025 14:59:46 +0800 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Patch v5 00/19] Support SIMD/eGPRs/SSP registers sampling for perf To: Ravi Bangoria Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Thomas Gleixner , Dave Hansen , Ian Rogers , Adrian Hunter , Jiri Olsa , Alexander Shishkin , Andi Kleen , Eranian Stephane , Mark Rutland , broonie@kernel.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Zide Chen , Falcon Thomas , Dapeng Mi , Xudong Hao References: <20251203065500.2597594-1-dapeng1.mi@linux.intel.com> Content-Language: en-US From: "Mi, Dapeng" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/16/2025 12:42 PM, Ravi Bangoria wrote: > Hi Dapeng, > >> While the hardware solution remains preferable due to its lower >> overhead and higher accuracy, this software approach provides a >> viable alternative. > Lower accuracy in the software approach is due to the delay in an NMI > delivery which will make the SIMD data misaligned a bit? Something like: > > insn1 > insn2 -> Overflow. RIP, GPRs captured by PEBS and NMI triggered > insn3 > insn4 > insn5 -> NMI delivered here, so SIMD regs are captured here? > insn6 > > Am I interpreting it correctly? Yes, there is always a delay with software-based (specifically PMI-based) sampling. Hardware-based sampling like PEBS is preferable when available. > > Thanks, > Ravi