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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 7000DC63777 for ; Fri, 20 Nov 2020 08:11:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E9E5322226 for ; Fri, 20 Nov 2020 08:11:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="PzJ3jlLW" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727042AbgKTIL0 (ORCPT ); Fri, 20 Nov 2020 03:11:26 -0500 Received: from mx2.suse.de ([195.135.220.15]:59024 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725942AbgKTILZ (ORCPT ); Fri, 20 Nov 2020 03:11:25 -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=1605859884; 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=POm2upnSpy8lgJ9BozivrNRInBH5i4/oOnz1KLQ0wVs=; b=PzJ3jlLWTN2U/kyBTyLSPcBdx1xw2KXRrDbXt6VoCLIpeyoxr02RjaSrVnquca5Hzcf+Rk Uno/i0l38a9XVd31/wRMsOY7MLATJC+fb0nwhT7t/aSdrc6wjPgeMVYBpmJqXXz0dI9yuy mCfK4/e04gdHAH0UFpztAkkGR2imKvo= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 204F7AB3D; Fri, 20 Nov 2020 08:11:24 +0000 (UTC) Date: Fri, 20 Nov 2020 09:11:23 +0100 From: Michal Hocko To: Muchun Song Cc: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, willy@infradead.org, osalvador@suse.de, song.bao.hua@hisilicon.com, duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v5 11/21] mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page Message-ID: <20201120081123.GC3200@dhcp22.suse.cz> References: <20201120064325.34492-1-songmuchun@bytedance.com> <20201120064325.34492-12-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201120064325.34492-12-songmuchun@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 20-11-20 14:43:15, Muchun Song wrote: [...] > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c > index eda7e3a0b67c..361c4174e222 100644 > --- a/mm/hugetlb_vmemmap.c > +++ b/mm/hugetlb_vmemmap.c > @@ -117,6 +117,8 @@ > #define RESERVE_VMEMMAP_NR 2U > #define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT) > #define TAIL_PAGE_REUSE -1 > +#define GFP_VMEMMAP_PAGE \ > + (GFP_KERNEL | __GFP_NOFAIL | __GFP_MEMALLOC) This is really dangerous! __GFP_MEMALLOC would allow a complete memory depletion. I am not even sure triggering the OOM killer is a reasonable behavior. It is just unexpected that shrinking a hugetlb pool can have destructive side effects. I believe it would be more reasonable to simply refuse to shrink the pool if we cannot free those pages up. This sucks as well but it isn't destructive at least. -- Michal Hocko SUSE Labs