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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C077AC433FE for ; Tue, 22 Feb 2022 09:53:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230094AbiBVJyA (ORCPT ); Tue, 22 Feb 2022 04:54:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229659AbiBVJx7 (ORCPT ); Tue, 22 Feb 2022 04:53:59 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B02FFD10B8; Tue, 22 Feb 2022 01:53:34 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5A6F8B81977; Tue, 22 Feb 2022 09:53:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8B258C340E8; Tue, 22 Feb 2022 09:53:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645523612; bh=T8Wutlu7mV5B3Pw57PVCDrO+l8i4LnewrOyADEDxSaI=; h=From:To:Cc:Subject:Date:In-Reply-To:From; b=mRv6omeV8naZHtnpCUkhTWsGNgpIqfA3TjW0E3YplZIVa0KAA6UGvNFFZrMPqj9Ap ARleDEaNRR0Bj6NGAMm8c8DnW0qjjp0MAU8hT7Bo5VDACT4TSQjY7yRRsDQDy4OW20 WL1nnyH729xq+5feCqoMVcz3b8j363aoXNQtQt5Ph5iwlfUy7BciwqjQzRB6QkmoKk VZUgIu1Y86yc91OQI/+fkYs1bH8OdNbHHTSTIYzgj+QSNSUPBVX5SbDcBSfKNL0non rP3OJEx7pUP8auNEINUcOHGC4FDoY6wXF+FdnzkyhlKzI6zhd0RgIWg7qlenLaXiZq pmxGOrlW3WZ2Q== From: SeongJae Park To: Jonghyeon Kim Cc: akpm@linux-foundation.org, 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: [RFC PATCH v1 2/3] mm/damon/core: Add damon_start_one() Date: Tue, 22 Feb 2022 09:53:28 +0000 Message-Id: <20220222095328.7962-1-sj@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220218102611.31895-3-tome01@ajou.ac.kr> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hello Jonghyeon, On Fri, 18 Feb 2022 19:26:10 +0900 Jonghyeon Kim wrote: > damon_start() function is designed to start multiple damon monitoring > contexts. But, sometimes we need to start monitoring one context. > Although __damon_start() could be considered to start for one monitoring > context, it seems reasonable to adopt a new function that does not need > to handle 'damon_lock' from the caller. > > Signed-off-by: Jonghyeon Kim > --- > include/linux/damon.h | 1 + > mm/damon/core.c | 25 +++++++++++++++++++++++++ > 2 files changed, 26 insertions(+) > > diff --git a/include/linux/damon.h b/include/linux/damon.h > index c0adf1566603..069577477662 100644 > --- a/include/linux/damon.h > +++ b/include/linux/damon.h > @@ -511,6 +511,7 @@ int damon_register_ops(struct damon_operations *ops); > int damon_select_ops(struct damon_ctx *ctx, enum damon_ops_id id); > > int damon_start(struct damon_ctx **ctxs, int nr_ctxs); > +int damon_start_one(struct damon_ctx *ctx); > int damon_stop(struct damon_ctx **ctxs, int nr_ctxs); > > #endif /* CONFIG_DAMON */ > diff --git a/mm/damon/core.c b/mm/damon/core.c > index 290c9c0535ee..e43f138a3489 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -466,6 +466,31 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs) > return err; > } > > +/** > + * damon_start_one() - Starts the monitorings for one context. > + * @ctx: monitoring context > + * > + * This function starts one monitoring thread for only one monitoring context > + * handling damon_lock. > + * > + * Return: 0 on success, negative error code otherwise. > + */ > +int damon_start_one(struct damon_ctx *ctx) > +{ > + int err = 0; > + > + mutex_lock(&damon_lock); > + err = __damon_start(ctx); > + if (err) { > + mutex_unlock(&damon_lock); > + return err; > + } > + nr_running_ctxs++; > + mutex_unlock(&damon_lock); > + > + return err; > +} > + IMHO, this looks like an unnecessary duplication of code. Unless this is needed for a real usecase, this change might unnecessarily make the code only a little bit more complicated. And to my understanding of the next patch, this is not really needed for this patchset. I will left comments on the patch. If I'm missing something, please clarify why this is really needed. Furthermore, damon_start() starts a set of DAMON contexts in exclusive manner, to ensure there will be no interference. This patch breaks the assumption. That is, contexts that started with damon_start() could be interfered by other contexts that started with damon_start_one(). I have a plan to make damon_start() also work for non-exclusive contexts group[1], though. [1] https://lore.kernel.org/linux-mm/20220217161938.8874-3-sj@kernel.org/ Thanks, SJ > /* > * __damon_stop() - Stops monitoring of given context. > * @ctx: monitoring context > -- > 2.17.1 >