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 820B4C433EF for ; Tue, 19 Oct 2021 10:03:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1A9AA61212 for ; Tue, 19 Oct 2021 10:03:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1A9AA61212 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 819186B006C; Tue, 19 Oct 2021 06:03:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7A2956B0071; Tue, 19 Oct 2021 06:03:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 69099900002; Tue, 19 Oct 2021 06:03:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0156.hostedemail.com [216.40.44.156]) by kanga.kvack.org (Postfix) with ESMTP id 5603D6B006C for ; Tue, 19 Oct 2021 06:03:41 -0400 (EDT) Received: from smtpin33.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 13F373C670 for ; Tue, 19 Oct 2021 10:03:41 +0000 (UTC) X-FDA: 78712750242.33.47EDADE Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf20.hostedemail.com (Postfix) with ESMTP id AAB27D0000AF for ; Tue, 19 Oct 2021 10:03:37 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 52DF661052; Tue, 19 Oct 2021 10:03:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1634637819; bh=6Y/Vzvlx9TgrQ9ag2k8mlYUT3QDwmIYd0+Q1ilrvvGk=; h=From:To:Cc:Subject:Date:In-Reply-To:From; b=iQBK42sSN93TduNEqIVoeyBv/C4SwJjMCr2+WdmsbvoABfgykRVf1PNtGH0lv3QU3 CsPne0wd1CDTK5qsOtixU/b7/z+3fiozjL8oPOP2gxKwdt/N3NvnzZsTz24rew9Smp QXRzbk5/bXKp5Zik784DTFITl174F/88AKEoqCcUO7+qqAXWbY60Eog7QlVS9K8OER dOKfmeCUziBVwIVHOS8pckLoVELef4QdWgHAszSt7ZsXvvs/NimTkse2reCUJX0swJ 4T5waW9jXbRhJbmpmesoGOzvBeC+F3pACVQEK67m/nSEhoSNtoASf8B9GCOlrC2jUK lfuMN0La16oZA== From: SeongJae Park To: Xin Hao Cc: sjpark@amazon.de, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/damon/core: Optimize kdamod.%d thread creation code Date: Tue, 19 Oct 2021 10:03:36 +0000 Message-Id: <20211019100336.5861-1-sj@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20211016165914.96049-1-xhao@linux.alibaba.com> Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=iQBK42sS; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of sj@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sj@kernel.org X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: AAB27D0000AF X-Stat-Signature: hfbyw963n5ufca8d34c8tgp9h1wb9ro1 X-HE-Tag: 1634637817-860224 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello Xin, On Sun, 17 Oct 2021 00:59:14 +0800 Xin Hao wrote: > When the ctx->adaptive_targets list is empty, > i did some test on monitor_on interface like this. > > echo on > /sys/kernel/debug/damon/monitor_on > [ 851.988307] damon: kdamond (5390) starts > > Though the ctx->adaptive_targets list is empty, but the > kthread_run still be called, and the kdamond.x thread still > be created, this is meaningless. Good finding, thank you! > > So there adds a judgment. only if the ctx->adaptive_targets > list is not empty, and ctx->kdamond pointer is NULL, then call > the __damon_start function. I think we cannot believe user-space users, but kernel-space API users. How about adding the check in 'dbgfs_monitor_on_write()' rather than '__damon_start()'? Also, apparently this patch is based on latest 'damon/next' branch of my tree. Could you please rebase this on latest -mm tree? Thanks, SJ [...]