From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753991Ab3BQWPH (ORCPT ); Sun, 17 Feb 2013 17:15:07 -0500 Received: from ozlabs.org ([203.10.76.45]:45019 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753289Ab3BQWPG (ORCPT ); Sun, 17 Feb 2013 17:15:06 -0500 From: Rusty Russell To: Andrew Morton , Johannes Weiner Cc: LKML , Nick Piggin , Stewart Smith , linux-mm@kvack.org, linux-arch@vger.kernel.org Subject: Re: [patch 1/2] mm: fincore() In-Reply-To: <20130215154235.0fb36f53.akpm@linux-foundation.org> References: <87a9rbh7b4.fsf@rustcorp.com.au> <20130211162701.GB13218@cmpxchg.org> <20130211141239.f4decf03.akpm@linux-foundation.org> <20130215063450.GA24047@cmpxchg.org> <20130215132738.c85c9eda.akpm@linux-foundation.org> <20130215231304.GB23930@cmpxchg.org> <20130215154235.0fb36f53.akpm@linux-foundation.org> User-Agent: Notmuch/0.14 (http://notmuchmail.org) Emacs/23.4.1 (i686-pc-linux-gnu) Date: Sat, 16 Feb 2013 14:53:43 +1030 Message-ID: <87621skhtc.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton writes: > On Fri, 15 Feb 2013 18:13:04 -0500 > Johannes Weiner wrote: >> I dunno. The byte vector might not be optimal but its worst cases >> seem more attractive, is just as extensible, and dead simple to use. > > But I think "which pages from this 4TB file are in core" will not be an > uncommon usage, and writing a gig of memory to find three pages is just > awful. Actually, I don't know of any usage for this call. I'd really like to use it for backup programs, so they stop pulling random crap into memory (but leave things already resident). But that needs to madvise(MADV_DONTNEED) on the page, so need mmap. So why not just use mincore? Cheers, Rusty.