From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95C07C433FE for ; Mon, 11 Oct 2021 21:02:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7581E60F43 for ; Mon, 11 Oct 2021 21:02:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235130AbhJKVEj (ORCPT ); Mon, 11 Oct 2021 17:04:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:36970 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230299AbhJKVEi (ORCPT ); Mon, 11 Oct 2021 17:04:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7E28360F23; Mon, 11 Oct 2021 21:02:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1633986158; bh=Jm6whGm1SYWN5n0xAQTdIeZ9V6XW0chF912C9+QjTcM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Nh65/IBIADLhMY9W1ThQ+x/HbV6CHO2s22TKn9rPlXzpLKdrKZHUpuZmVEbFmB1Ws 7yfK4ne8BH9vrfsfviIBXtPVE7Z4/Md8m7I4tXLACBdAKbsd3Y2C7QMIhJWNDtKIic SB2TZau4xVB2gZiPlaimrGkh72Ut4efN4vhaKofU= Date: Mon, 11 Oct 2021 14:02:35 -0700 From: Andrew Morton To: SeongJae Park Cc: Jonathan.Cameron@Huawei.com, amit@kernel.org, benh@kernel.crashing.org, corbet@lwn.net, david@redhat.com, dwmw@amazon.com, elver@google.com, foersleo@amazon.de, gthelen@google.com, markubo@amazon.de, rientjes@google.com, shakeelb@google.com, shuah@kernel.org, linux-damon@amazon.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] mm/damon/dbgfs: Implement recording feature Message-Id: <20211011140235.f75b842f861b730c53e4b19c@linux-foundation.org> In-Reply-To: <20211011093057.30790-1-sj@kernel.org> References: <20211010150140.be96f07048079188d9d6b613@linux-foundation.org> <20211011093057.30790-1-sj@kernel.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 11 Oct 2021 09:30:57 +0000 SeongJae Park wrote: > Hello Andrew, > > > Thank you for great questions! > > On Sun, 10 Oct 2021 15:01:40 -0700 Andrew Morton wrote: > > > On Fri, 8 Oct 2021 09:45:06 +0000 SeongJae Park wrote: > > > > > The user space can get the monitoring results via the 'damon_aggregated' > > > tracepoint event. For simplicity and brevity, the tracepoint events > > > have some duplicated information such as 'target_id' and 'nr_regions', > > > though. As a result, its size is greater than really needed. Also, > > > dealing with the tracepoint could be complex for some simple use cases. > > > To provide a way for getting more efficient and simple monitoring > > > results to user space, this commit implements 'recording' feature in > > > 'damon-dbgfs'. > > > > > > The feature is exported to the user space via a new debugfs file named > > > 'record', which is located in '/damon/' directory. The file > > > allows users to record monitored access patterns in a regular binary > > > file in a simple format. > > > > Binary files are troublesome. > > > > Is the format of this file documented anywhere? > > No. I intended the Python script in the following patch[1] and the user space > tool[2] to be used as such documents. I will write up one before the next > spin. > > [1] https://lore.kernel.org/linux-mm/20211008094509.16179-3-sj@kernel.org/ > [2] https://github.com/awslabs/damo/blob/v0.0.5/_damon_result.py#L38 > > > > > I assume that the file's contents will have different representations > > depending on host endianness and word size and I further assume that > > the provided python script won't handle this very well? > > You're right. I will make the script properly handle the cases in the next > spin. Well, rather than messing with the different file formats, you could make the binary file machine-independent. Decide on the endianness and word size, implement them and document them. Things like cpu_to_le32 are zero-cost on little-endian machines.