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To: Michal Hocko Cc: Andrew Morton , Chris Metcalf , Rusty Russell , linux-mm@kvack.org, Guenter Roeck References: <1549533189-9177-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20190212101109.GB7584@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: <82168e14-8a89-e6ac-1756-e473e9c21616@i-love.sakura.ne.jp> Date: Tue, 12 Feb 2019 19:25:46 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <20190212101109.GB7584@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 2019/02/12 19:11, Michal Hocko wrote: > This patch is ugly as hell! I do agree that for_each_cpu not working on > CONFIG_SMP=n sucks but why do we even care about lru_add_drain_all when > there is a single cpu? Why don't we simply do > > diff --git a/mm/swap.c b/mm/swap.c > index aa483719922e..952f24b09070 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -660,6 +660,7 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy) > > static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); > > +#ifdef CONFIG_SMP > /* > * Doesn't need any cpu hotplug locking because we do rely on per-cpu > * kworkers being shut down before our page_alloc_cpu_dead callback is > @@ -702,6 +703,10 @@ void lru_add_drain_all(void) > > mutex_unlock(&lock); > } > +#else > +#define lru_add_drain_all() lru_add_drain() > + > +#endif If there is no need to evaluate the "if" conditions, I'm fine with this shortcut.