From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f41.google.com (mail-wg0-f41.google.com [74.125.82.41]) by kanga.kvack.org (Postfix) with ESMTP id ED1EC6B0031 for ; Tue, 1 Jul 2014 16:15:53 -0400 (EDT) Received: by mail-wg0-f41.google.com with SMTP id a1so10208987wgh.12 for ; Tue, 01 Jul 2014 13:15:53 -0700 (PDT) Received: from kirsi1.inet.fi (mta-out1.inet.fi. [62.71.2.199]) by mx.google.com with ESMTP id t3si29400832wju.44.2014.07.01.13.15.52 for ; Tue, 01 Jul 2014 13:15:52 -0700 (PDT) Date: Tue, 1 Jul 2014 23:15:40 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH] rmap: fix pgoff calculation to handle hugepage correctly Message-ID: <20140701201540.GA5953@node.dhcp.inet.fi> References: <1404225982-22739-1-git-send-email-n-horiguchi@ah.jp.nec.com> <20140701180739.GA4985@node.dhcp.inet.fi> <20140701185021.GA10356@nhori.bos.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140701185021.GA10356@nhori.bos.redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Andrew Morton , Joonsoo Kim , Hugh Dickins , Rik van Riel , Hillf Danton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Naoya Horiguchi On Tue, Jul 01, 2014 at 02:50:21PM -0400, Naoya Horiguchi wrote: > On Tue, Jul 01, 2014 at 09:07:39PM +0300, Kirill A. Shutemov wrote: > > Why do we need this special case for hugetlb page ->index? Why not use > > PAGE_SIZE units there too? Or I miss something? > > hugetlb pages are never split, so we use larger page cache size for > hugetlbfs file (to avoid large sparse page cache tree.) For transparent huge page cache I would like to have native support in page cache radix-tree: since huge pages are always naturally aligned we can create a leaf node for it several (RADIX_TREE_MAP_SHIFT - HPAGE_PMD_ORDER) levels up by tree, which would cover all indexes in the range the huge page represents. This approach should fit hugetlb too. And -1 special case for hugetlb. But I'm not sure when I'll get time to play with this... -- Kirill A. Shutemov -- 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