From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f197.google.com (mail-qk0-f197.google.com [209.85.220.197]) by kanga.kvack.org (Postfix) with ESMTP id 3B9196B000D for ; Thu, 1 Mar 2018 10:03:11 -0500 (EST) Received: by mail-qk0-f197.google.com with SMTP id f143so4893312qke.12 for ; Thu, 01 Mar 2018 07:03:11 -0800 (PST) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id e56si4644433qtk.321.2018.03.01.07.03.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Mar 2018 07:03:10 -0800 (PST) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w21F0qWg112602 for ; Thu, 1 Mar 2018 10:03:09 -0500 Received: from e06smtp15.uk.ibm.com (e06smtp15.uk.ibm.com [195.75.94.111]) by mx0b-001b2d01.pphosted.com with ESMTP id 2gek14th8e-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 01 Mar 2018 10:03:08 -0500 Received: from localhost by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 1 Mar 2018 15:03:03 -0000 Date: Thu, 1 Mar 2018 16:02:58 +0100 From: Martin Schwidefsky Subject: Re: [PATCH v3 0/4] Split page_type out from mapcount In-Reply-To: <20180301145058.GA19662@bombadil.infradead.org> References: <20180228223157.9281-1-willy@infradead.org> <20180301081750.42b135c3@mschwideX1> <20180301124412.gm6jxwzyfskzxspa@node.shutemov.name> <20180301145058.GA19662@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20180301160258.6a619212@mschwideX1> Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: "Kirill A. Shutemov" , linux-mm@kvack.org, Matthew Wilcox , linux-kernel@vger.kernel.org On Thu, 1 Mar 2018 06:50:58 -0800 Matthew Wilcox wrote: > On Thu, Mar 01, 2018 at 03:44:12PM +0300, Kirill A. Shutemov wrote: > > On Thu, Mar 01, 2018 at 08:17:50AM +0100, Martin Schwidefsky wrote: > > > Yeah, that is a nasty bit of code. On s390 we have 2K page tables (pte) > > > but 4K pages. If we use full pages for the pte tables we waste 2K of > > > memory for each of the tables. So we allocate 4K and split it into two > > > 2K pieces. Now we have to keep track of the pieces to be able to free > > > them again. > > > > Have you considered to use slab for page table allocation instead? > > IIRC some architectures practice this already. > > You're not allowed to do that any more. Look at pgtable_page_ctor(), > or rather ptlock_init(). Oh yes, I forgot about the ptl. This takes up some fields in struct page which the slab/slub cache want to use as well. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org