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 876EFC433FE for ; Wed, 12 Jan 2022 10:18:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352451AbiALKR7 (ORCPT ); Wed, 12 Jan 2022 05:17:59 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:34614 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346594AbiALKR4 (ORCPT ); Wed, 12 Jan 2022 05:17:56 -0500 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id AF6DE1F3D0; Wed, 12 Jan 2022 10:17:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1641982675; h=from:from:reply-to: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=g/PcfchBevR47yLCk2MvJMcIoOeey+Dc7tFuclOHyHY=; b=ihOEkN8DjQyUt0ipnU90uMOZ2gXOVMRbLDzXwZb6s6F8FLHvme9bzA1Up283oRsVgW8TRI 3snyjvVlAjeBn09Iscu8aTJ2GMnUcRLx0jwB0ZIVXuvPDja9V5BdcKNwCLFIhyLOFsuMpE lL6uy541yhuj4resrieM6V346Nz/eO4= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 71453A3B81; Wed, 12 Jan 2022 10:17:54 +0000 (UTC) Date: Wed, 12 Jan 2022 11:17:53 +0100 From: Michal Hocko To: Yu Zhao Cc: Andrew Morton , Linus Torvalds , Andi Kleen , Catalin Marinas , Dave Hansen , Hillf Danton , Jens Axboe , Jesse Barnes , Johannes Weiner , Jonathan Corbet , Matthew Wilcox , Mel Gorman , Michael Larabel , Rik van Riel , Vlastimil Babka , Will Deacon , Ying Huang , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, page-reclaim@google.com, x86@kernel.org, Konstantin Kharlamov Subject: Re: [PATCH v6 6/9] mm: multigenerational lru: aging Message-ID: References: <20220104202227.2903605-1-yuzhao@google.com> <20220104202227.2903605-7-yuzhao@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 11-01-22 18:01:29, Yu Zhao wrote: > On Mon, Jan 10, 2022 at 05:57:39PM +0100, Michal Hocko wrote: > > On Tue 04-01-22 13:22:25, Yu Zhao wrote: > > [...] > > > +static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk) > > > +{ > > > + static const struct mm_walk_ops mm_walk_ops = { > > > + .test_walk = should_skip_vma, > > > + .p4d_entry = walk_pud_range, > > > + }; > > > + > > > + int err; > > > +#ifdef CONFIG_MEMCG > > > + struct mem_cgroup *memcg = lruvec_memcg(lruvec); > > > +#endif > > > + > > > + walk->next_addr = FIRST_USER_ADDRESS; > > > + > > > + do { > > > + unsigned long start = walk->next_addr; > > > + unsigned long end = mm->highest_vm_end; > > > + > > > + err = -EBUSY; > > > + > > > + rcu_read_lock(); > > > +#ifdef CONFIG_MEMCG > > > + if (memcg && atomic_read(&memcg->moving_account)) > > > + goto contended; > > > +#endif > > > > Why do you need to check for moving_account? > > This check, if succeeds, blocks memcg migration. OK, I can see that you rely on the RCU here for the synchronization. A comment which mentions mem_cgroup_move_charge would be helpful for clarity. Is there any reason you are not using folio_memcg_lock in the pte walk instead? -- Michal Hocko SUSE Labs