From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 377B422332E; Mon, 10 Mar 2025 15:50:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741621823; cv=none; b=SRwP5uaJPoIxhPBu1+gE/qbXFcCYrbEp5twdebpHmPEEsQUUAUKmgtvOn4ho5jevtqMMs4opnqUcvXJSbT7/cOaaArqlKPumMtxF5dxMlXb1DQvowqQV9vqqN/Fy5phQLKDDtjMNrtwt/yiP1pWROHYuasRWhOeRViOGzfV6/Sg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741621823; c=relaxed/simple; bh=iS9+vSvOzrqV62mxwznPJsltsTrjWHcYTR8pofdi0Q8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LHPyqYZQsfMe8tdvpFaRz/YFP/A2Iej5dXnxtxSRTjOknZRqnYDvTV+DO26nMhh8FBi1sslqZxuLDvoOoNS7pKazUn9VD+E4nkXTwlPqyVmvrOkrkQbHGJLj5c+KX/M6qezmdgjqfQA1VkRRDdUb7xh5uBKhaSmUDdEPTOQ0snI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6EF4E1692; Mon, 10 Mar 2025 08:50:31 -0700 (PDT) Received: from localhost (e132581.arm.com [10.1.196.87]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 96B003F5A1; Mon, 10 Mar 2025 08:50:19 -0700 (PDT) Date: Mon, 10 Mar 2025 15:50:15 +0000 From: Leo Yan To: Suzuki K Poulose Cc: Mike Leach , James Clark , Jonathan Corbet , Alexander Shishkin , Arnaldo Carvalho de Melo , Namhyung Kim , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 5/8] coresight: etm: Add an attribute for updating buffer Message-ID: <20250310155015.GG9682@e132581.arm.com> References: <20250310104919.58816-1-leo.yan@arm.com> <20250310104919.58816-6-leo.yan@arm.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Mar 10, 2025 at 01:29:26PM +0000, Suzuki Kuruppassery Poulose wrote: > Hi Leo > > On 10/03/2025 10:49, Leo Yan wrote: > > Add an attribute for updating buffer when the AUX trace is paused. And > > populate the value to the 'update_buf_on_pause' flag during the AUX > > setting up. > > Do we need this attribute in the uAPI ? This uAPI allows users to perform AUX pause and resume without the long latency caused by copying hardware trace data. E.g., a user can specify a large AUX buffer size using option "-m,128M". If the buffer is considered large enough to accommodate hardware trace data for a small program, the 'update_buf_on_pause' flag can be set to false, the copying will be deferred until the end of the perf session. I am bias to keep this uAPI. If you prefer to remove it, I am also fine with that. > Could we do this by default for > sinks without interrupt ? This definitely improves the quality of trace > collected for such sinks and the driver can transparently do this. How about we dynamically set the default flag in the Perf tool? - If users set explictly the 'update_buf_on_pause' flag, then the setting will be respected. - If users don't set the flag, perf tool detects it is TRBE sinks, then it can set 'update_buf_on_pause' flag as false. - If users don't set the flag, perf tool detects it is ETF/ETB/ETR sinks, it sets the flag as true. Thanks, Leo