From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f198.google.com (mail-pg1-f198.google.com [209.85.215.198]) by kanga.kvack.org (Postfix) with ESMTP id 563236B04D6 for ; Tue, 30 Oct 2018 02:56:02 -0400 (EDT) Received: by mail-pg1-f198.google.com with SMTP id t3-v6so7910033pgp.0 for ; Mon, 29 Oct 2018 23:56:02 -0700 (PDT) Received: from mailgw01.mediatek.com ([210.61.82.183]) by mx.google.com with ESMTPS id c41-v6si10588037plj.194.2018.10.29.23.56.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Oct 2018 23:56:01 -0700 (PDT) Message-ID: <1540882551.23278.12.camel@mtkswgap22> Subject: Re: [PATCH v3] mm/page_owner: use kvmalloc instead of kmalloc From: Miles Chen 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" Content-Transfer-Encoding: 7bit MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Joe Perches , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com 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().