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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0302CC433E0 for ; Mon, 15 Feb 2021 19:40:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BE9BA64E30 for ; Mon, 15 Feb 2021 19:40:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230232AbhBOTkW (ORCPT ); Mon, 15 Feb 2021 14:40:22 -0500 Received: from mx2.suse.de ([195.135.220.15]:54108 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230098AbhBOTkD (ORCPT ); Mon, 15 Feb 2021 14:40:03 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1613417957; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Fx2cr07cmhwLgVLKoMIL0c93fXgTqa4GArm3bCqwx58=; b=gmTzrbK2+uwQ0IULYjwTpZT7v8vs5KhYk9UoGVvxF/J51TVevzHw+bL/LFKeTPWTkK4woE 93/CuIfpEbenm1Odqa3C2PLHH7jGrJ8I2jSce3cYUWBJh5fsXETgfRVFc2vaT9YnHGtX6W v/lZPWRPIyz1VR0+PmlB/NMWpRX2NUo= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C133DAD29; Mon, 15 Feb 2021 19:39:16 +0000 (UTC) Date: Mon, 15 Feb 2021 20:39:15 +0100 From: Michal Hocko To: Muchun Song Cc: Jonathan Corbet , Mike Kravetz , Thomas Gleixner , mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, Peter Zijlstra , viro@zeniv.linux.org.uk, Andrew Morton , paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, Randy Dunlap , oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, Mina Almasry , David Rientjes , Matthew Wilcox , Oscar Salvador , "Song Bao Hua (Barry Song)" , David Hildenbrand , HORIGUCHI =?utf-8?B?TkFPWUEo5aCA5Y+jIOebtOS5nyk=?= , Joao Martins , Xiongchun duan , linux-doc@vger.kernel.org, LKML , Linux Memory Management List , linux-fsdevel Subject: Re: [External] Re: [PATCH v15 4/8] mm: hugetlb: alloc the vmemmap pages associated with each HugeTLB page Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 16-02-21 02:19:20, Muchun Song wrote: > On Tue, Feb 16, 2021 at 1:48 AM Muchun Song wrote: > > > > On Tue, Feb 16, 2021 at 12:28 AM Michal Hocko wrote: > > > > > > On Mon 15-02-21 23:36:49, Muchun Song wrote: > > > [...] > > > > > There shouldn't be any real reason why the memory allocation for > > > > > vmemmaps, or handling vmemmap in general, has to be done from within the > > > > > hugetlb lock and therefore requiring a non-sleeping semantic. All that > > > > > can be deferred to a more relaxed context. If you want to make a > > > > > > > > Yeah, you are right. We can put the freeing hugetlb routine to a > > > > workqueue. Just like I do in the previous version (before v13) patch. > > > > I will pick up these patches. > > > > > > I haven't seen your v13 and I will unlikely have time to revisit that > > > version. I just wanted to point out that the actual allocation doesn't > > > have to happen from under the spinlock. There are multiple ways to go > > > around that. Dropping the lock would be one of them. Preallocation > > > before the spin lock is taken is another. WQ is certainly an option but > > > I would take it as the last resort when other paths are not feasible. > > > > > > > "Dropping the lock" and "Preallocation before the spin lock" can limit > > the context of put_page to non-atomic context. I am not sure if there > > is a page puted somewhere under an atomic context. e.g. compaction. > > I am not an expert on this. > > Using GFP_KERNEL will also use the current task cpuset to allocate > memory. Do we have an interface to ignore current task cpuset？If not, > WQ may be the only option and it also will not limit the context of > put_page. Right? Well, GFP_KERNEL is constrained to the task cpuset only if the said cpuset is hardwalled IIRC. But I do not see why this is a problem. -- Michal Hocko SUSE Labs