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d=linutronix.de; s=2020e; t=1661349011; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=lxmXEz446Sqnmo7KcG5N2T9SivEVa9HXVqWIhBMNFOU=; b=QAKKYr/DzS3nyL69DUgS/aGsBL0v0xdMxE+TpnUuI3oliBHyJW7GbWwMX1QYAAcpf1iWDf O8b+HdQL5nzs5ZCQ== To: Rasmus Villemoes , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Steven Rostedt , Linus Torvalds , Matthew Wilcox , Andrew Morton , Nick Terrell , linux-mm@kvack.org Subject: Re: [PATCH 7/9] mm/compaction: Get rid of RT ifdeffery In-Reply-To: <54a68cad-f15d-bef2-8627-3d3bfb6f030d@prevas.dk> References: <20220817162703.728679-1-bigeasy@linutronix.de> <20220817162703.728679-8-bigeasy@linutronix.de> <54a68cad-f15d-bef2-8627-3d3bfb6f030d@prevas.dk> Date: Wed, 24 Aug 2022 15:50:10 +0200 Message-ID: <871qt5zr71.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; 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dkim=pass header.d=linutronix.de header.s=2020 header.b=Y9CwXl5t; dkim=pass header.d=linutronix.de header.s=2020e header.b="QAKKYr/D"; spf=pass (imf21.hostedemail.com: domain of tglx@linutronix.de designates 193.142.43.55 as permitted sender) smtp.mailfrom=tglx@linutronix.de; dmarc=pass (policy=none) header.from=linutronix.de X-HE-Tag: 1661349013-207877 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: On Thu, Aug 18 2022 at 10:55, Rasmus Villemoes wrote: > On 17/08/2022 18.27, Sebastian Andrzej Siewior wrote: >> -#ifdef CONFIG_PREEMPT_RT >> -int sysctl_compact_unevictable_allowed __read_mostly = 0; >> -#else >> -int sysctl_compact_unevictable_allowed __read_mostly = 1; >> -#endif >> +int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT; > > Why introduce a Kconfig symbol for this, and not just spell the > initializer "IS_ENABLED(CONFIG_PREEMPT_RT) ? 0 : 1" or simply > "!IS_ENABLED(CONFIG_PREEMPT_RT)"? The reason for the config symbol is that Linus requested to have semantically obvious constructs which can be utilized even without RT and clearly spell out what the construct does. When RT selects this then it's a documented requirement/dependency. > And if you do keep it in Kconfig, shouldn't the symbol be "depends on > COMPACTION" so it doesn't needlessly appear in .config when > !CONFIG_COMPACTION. Sure. Thanks, tglx