From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx157.postini.com [74.125.245.157]) by kanga.kvack.org (Postfix) with SMTP id D71E66B0002 for ; Sun, 17 Feb 2013 17:56:08 -0500 (EST) Date: Sun, 17 Feb 2013 14:54:56 -0800 From: Andrew Morton Subject: Re: [patch 1/2] mm: fincore() Message-Id: <20130217145456.375dab11.akpm@linux-foundation.org> In-Reply-To: <87621skhtc.fsf@rustcorp.com.au> 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-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rusty Russell Cc: Johannes Weiner , LKML , Nick Piggin , Stewart Smith , linux-mm@kvack.org, linux-arch@vger.kernel.org On Sat, 16 Feb 2013 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. That's good news ;) We shouldn't add it unless there's damn good reason. > 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? One can use fadvise(POSIX_FADV_DONTNEED) to drop the pages. Or toss your backup app into a small memcg so it reclaims its own stuff. See recent thread "mm: fadvise: Drain all pagevecs if POSIX_FADV_DONTNEED fails to discard all pages" -- 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