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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 3AC82C6786F for ; Tue, 30 Oct 2018 06:56:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E7C02082D for ; Tue, 30 Oct 2018 06:56:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E7C02082D 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 S1727547AbeJ3PsT (ORCPT ); Tue, 30 Oct 2018 11:48:19 -0400 Received: from mailgw01.mediatek.com ([210.61.82.183]:63313 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1727501AbeJ3PsS (ORCPT ); Tue, 30 Oct 2018 11:48:18 -0400 X-UUID: fce3c53b849b4bad842c84424a684b20-20181030 X-UUID: fce3c53b849b4bad842c84424a684b20-20181030 Received: from mtkcas06.mediatek.inc [(172.21.101.30)] by mailgw01.mediatek.com (envelope-from ) (mhqrelay.mediatek.com ESMTP with TLS) with ESMTP id 1840357904; Tue, 30 Oct 2018 14:55:53 +0800 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs03n2.mediatek.inc (172.21.101.182) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Tue, 30 Oct 2018 14:55:51 +0800 Received: from [172.21.77.33] (172.21.77.33) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Tue, 30 Oct 2018 14:55:51 +0800 Message-ID: <1540882551.23278.12.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 14:55:51 +0800 In-Reply-To: <20181030060601.GR32673@dhcp22.suse.cz> References: <1540790176-32339-1-git-send-email-miles.chen@mediatek.com> <20181029080708.GA32673@dhcp22.suse.cz> <20181029081706.GC32673@dhcp22.suse.cz> <1540862950.12374.40.camel@mtkswgap22> <20181030060601.GR32673@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: 2E26B09DC99F707EAE83DE70B9D57D6161CD602C3CEB5221A275CD5945312BFA2000:8 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2018-10-30 at 07:06 +0100, Michal Hocko wrote: > On Tue 30-10-18 09:29:10, Miles Chen wrote: > > 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. > > If you mean for this particular situation then is this really worth > it? I mean this is a short term allocation for root only so you do not > have to worry about low mem depletion. The 1...3 are applied to print_page_owner(), not in kmalloc() or kvmalloc() logic. It's a real problem when using page_owner. I found this issue recently: I'm not able to read page_owner information during a overnight test. (error: read failed: Out of memory). I replace kmalloc() with vmalloc() and it worked well. > > If you are thiking in more generic terms to allow kmalloc to use highmem > then I am not really sure this will work out. I'm thinking about modify print_page_owner().