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 229DEC4332B for ; Wed, 17 Feb 2021 13:33:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F32C164EBB for ; Wed, 17 Feb 2021 13:33:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233171AbhBQNdM (ORCPT ); Wed, 17 Feb 2021 08:33:12 -0500 Received: from mx2.suse.de ([195.135.220.15]:39996 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233061AbhBQNbb (ORCPT ); Wed, 17 Feb 2021 08:31:31 -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=1613568645; 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=SETwTKFY3v+orwvahxTNxIwQK9vE3JMDX1v8ML7p/dI=; b=N1vhK3c89g1umX8EeWbZlXuiLIAD7rTi0xuYJtvpD8m11GMxlzz3PV1pHcythf0W0H3LW5 vVOkYKXZhzctrn0bzDJwrpdKyFB14tgs8hCzm0Mx/vSyrKE5NkvRakLmc9P7YhFFjCDLVE cdlv2ka8MLG3rUmjVvsJ3Xa6jwKDFL4= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 1D265B1D7; Wed, 17 Feb 2021 13:30:45 +0000 (UTC) Date: Wed, 17 Feb 2021 14:30:43 +0100 From: Michal Hocko To: Oscar Salvador Cc: Andrew Morton , Mike Kravetz , David Hildenbrand , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm: Make alloc_contig_range handle free hugetlb pages Message-ID: References: <20210217100816.28860-1-osalvador@suse.de> <20210217100816.28860-2-osalvador@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210217100816.28860-2-osalvador@suse.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 17-02-21 11:08:15, Oscar Salvador wrote: > Free hugetlb pages are tricky to handle so as to no userspace application > notices disruption, we need to replace the current free hugepage with > a new one. > > In order to do that, a new function called alloc_and_dissolve_huge_page > is introduced. > This function will first try to get a new fresh hugetlb page, and if it > succeeds, it will dissolve the old one. > > With regard to the allocation, since we do not know whether the old page > was allocated on a specific node on request, the node the old page belongs > to will be tried first, and then we will fallback to all nodes containing > memory (N_MEMORY). I do not think fallback to a different zone is ok. If yes then this really requires a very good reasoning. alloc_contig_range is an optimistic allocation interface at best and it shouldn't break carefully node aware preallocation done by administrator. > Note that gigantic hugetlb pages are fenced off since there is a cyclic > dependency between them and alloc_contig_range. Why do we need/want to do all this in the first place? -- Michal Hocko SUSE Labs