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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham 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 57FEAC0044C for ; Tue, 30 Oct 2018 01:29:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11C212082D for ; Tue, 30 Oct 2018 01:29:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 11C212082D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mediatek.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726136AbeJ3KUv (ORCPT ); Tue, 30 Oct 2018 06:20:51 -0400 Received: from mailgw02.mediatek.com ([210.61.82.184]:35479 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1725902AbeJ3KUv (ORCPT ); Tue, 30 Oct 2018 06:20:51 -0400 X-UUID: bf4319f52ccb49e6a55b67a58e6a52da-20181030 X-UUID: bf4319f52ccb49e6a55b67a58e6a52da-20181030 Received: from mtkcas09.mediatek.inc [(172.21.101.178)] by mailgw02.mediatek.com (envelope-from ) (mhqrelay.mediatek.com ESMTP with TLS) with ESMTP id 1095696761; Tue, 30 Oct 2018 09:29:12 +0800 Received: from mtkcas07.mediatek.inc (172.21.101.84) by mtkmbs03n2.mediatek.inc (172.21.101.182) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Tue, 30 Oct 2018 09:29:10 +0800 Received: from [172.21.77.33] (172.21.77.33) by mtkcas07.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Tue, 30 Oct 2018 09:29:10 +0800 Message-ID: <1540862950.12374.40.camel@mtkswgap22> Subject: Re: [PATCH v3] mm/page_owner: use kvmalloc instead of kmalloc From: Miles Chen To: Michal Hocko CC: Andrew Morton , Joe Perches , Matthew Wilcox , , , , , Date: Tue, 30 Oct 2018 09:29:10 +0800 In-Reply-To: <20181029081706.GC32673@dhcp22.suse.cz> References: <1540790176-32339-1-git-send-email-miles.chen@mediatek.com> <20181029080708.GA32673@dhcp22.suse.cz> <20181029081706.GC32673@dhcp22.suse.cz> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-TM-SNTS-SMTP: E2CBA49B416C4E3BC132CB3C34AA7BF195474575720F322FAF6EEBF393DA96F42000:8 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2018-10-29 at 09:17 +0100, Michal Hocko wrote: > On Mon 29-10-18 09:07:08, Michal Hocko wrote: > [...] > > Besides that, the following doesn't make much sense to me. It simply > > makes no sense to use vmalloc for sub page allocation regardless of > > HIGHMEM. > > OK, it is still early morning here. Now I get the point of the patch. > You just want to (ab)use highmeme for smaller requests. I do not like > this, to be honest. It causes an internal fragmentation and more > importantly the VMALLOC space on 32b where HIGHMEM is enabled (do we > have any 64b with HIGHMEM btw?) is quite small to be wasted like that. > thanks for your comment. It looks like that using vmalloc fallback for sub page allocation is not good here. Your comment gave another idea: 1. force kbuf to PAGE_SIZE 2. allocate a page by alloc_page(GFP_KERNEL | __GFP_HIGHMEM); so we can get a highmem page if possible 3. use kmap/kunmap pair to create mapping for this page. No vmalloc space is used. 4. do not change kvmalloc logic. > In any case such a changes should come with some numbers and as a > separate patch for sure. > > > > diff --git a/mm/util.c b/mm/util.c > > > index 8bf08b5b5760..7b1c59b9bfbf 100644 > > > --- a/mm/util.c > > > +++ b/mm/util.c > > > @@ -416,10 +416,10 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node) > > > ret = kmalloc_node(size, kmalloc_flags, node); > > > > > > /* > > > - * It doesn't really make sense to fallback to vmalloc for sub page > > > - * requests > > > + * It only makes sense to fallback to vmalloc for sub page > > > + * requests if we might be able to allocate highmem pages. > > > */ > > > - if (ret || size <= PAGE_SIZE) > > > + if (ret || (!IS_ENABLED(CONFIG_HIGHMEM) && size <= PAGE_SIZE)) > > > return ret; > > > > > > return __vmalloc_node_flags_caller(size, node, flags, > > > -- > > > 2.18.0 > > > > > > > -- > > Michal Hocko > > SUSE Labs >