From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) (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 80646130A57; Tue, 16 Apr 2024 14:48:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=167.114.26.122 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713278938; cv=none; b=mhCdrZF5bIx2IGVixWub4Vy1VmP6vJH7nxeXHQ4eKxUGngHiXZzYQLAyBo/oGoaMr1i7rZV7/dmvqMRixITEybEnHhgeddNlgf7Xiedwb9675hSsllVXDZqqOS/RCOn9NbcMedxXJOYmy8FCZpWnXrspeBExnWj/wSho9KCmSfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713278938; c=relaxed/simple; bh=XASMDrMQqjDqU0d0fbKxtJY6C1GYjAaFpOo2re1urus=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OEWER7z8K+DuUY+nt0zG81Nxr2me8YNvJnas3jJdDmL1Z/GiwhPg1IWn7fzEQilcrrNS9zsDa4QSyq60lOk0ptfFb7hL0Ut8dy0BjvFx46ANSp1XUpj13hv8dQH2G5hckOzXhUAArbSVMWfRytZS+LL9nSintOyn3wHW4AZ2xUQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b=myYs6w9+; arc=none smtp.client-ip=167.114.26.122 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="myYs6w9+" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1713278935; bh=XASMDrMQqjDqU0d0fbKxtJY6C1GYjAaFpOo2re1urus=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=myYs6w9+hwAIAfwbR6flzjGY65R7Gnln+E8J77MNplcUCk0+vGNs5COWL1pszRVtk Il8WwjodaoIM+D92vBnQX9s+/ILu1PSIdXABIR9HQvCdLQPWDbcR7a29oHRYpS8+lb RW3JmvRBtn5BO5NkkRRQEaEIUV0Gs75TTAqhwFBQ1EGC0DNR0RkZnVzEthzjFLMTfU X+PfalRiHJMN3LNuu+4CB74DSnSotC3dkxzteQWM2jbxDWSbDcj0VZOkPMTxhbaYcH t1S8D1nBgELojLS6RqsctbxLck/UJx82L15JESRj/d9J2xWb87/YMXJrNZmYxa5awR J9L2ghGANhTHg== Received: from [172.16.0.134] (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4VJn3q2xw3zw7j; Tue, 16 Apr 2024 10:48:55 -0400 (EDT) Message-ID: <46859f90-bdf6-4502-bf6a-4add6dad3668@efficios.com> Date: Tue, 16 Apr 2024 10:48:57 -0400 Precedence: bulk X-Mailing-List: linux-trace-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: RFC: using NIC DMA ring as tracing buffer? To: Alexander Aring , linux-trace-devel@vger.kernel.org Cc: linux-trace-users@vger.kernel.org References: From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024-04-16 10:41, Alexander Aring wrote: > Hi all, > > I have an idea about using the DMA rings of a networking card as a > tracing buffer. The first thing I'd be worried about is overhead caused by false-sharing if you trace a large SMP/many-core system all into the same global NIC buffer. The cache lines will bounce left and right which is bad performance-wise. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com