From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966730Ab3E2PDR (ORCPT ); Wed, 29 May 2013 11:03:17 -0400 Received: from mail.anarazel.de ([217.115.131.40]:48339 "EHLO mail.anarazel.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966617Ab3E2PDN (ORCPT ); Wed, 29 May 2013 11:03:13 -0400 X-Greylist: delayed 596 seconds by postgrey-1.27 at vger.kernel.org; Wed, 29 May 2013 11:03:13 EDT Date: Wed, 29 May 2013 16:53:12 +0200 From: Andres Freund To: Rusty Russell Cc: Andrew Morton , Johannes Weiner , LKML , Nick Piggin , Stewart Smith , linux-mm@kvack.org, linux-arch@vger.kernel.org Subject: Re: [patch 1/2] mm: fincore() Message-ID: <20130529145312.GE3955@alap2.anarazel.de> 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> <87621skhtc.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87621skhtc.fsf@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2013-02-16 14:53:43 +1030, Rusty Russell wrote: > 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. [months later, catching up] I do. Postgres' could really use something like that for making saner assumptions about the cost of doing an index/heap scan. postgres doesn't use mmap() and mmaping larger files into memory isn't all that cheap (32bit...) so having fincore would be nice. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services