From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262747AbVCJRrZ (ORCPT ); Thu, 10 Mar 2005 12:47:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262677AbVCJRmP (ORCPT ); Thu, 10 Mar 2005 12:42:15 -0500 Received: from e32.co.us.ibm.com ([32.97.110.130]:9909 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S262729AbVCJRiD (ORCPT ); Thu, 10 Mar 2005 12:38:03 -0500 Subject: Re: [PATCH] 0/2 Buddy allocator with placement policy (Version 9) + prezeroing (Version 4) From: Dave Hansen To: Mel Gorman Cc: linux-mm , Linux Kernel Mailing List In-Reply-To: References: <20050307193938.0935EE594@skynet.csn.ul.ie> <1110239966.6446.66.camel@localhost> Content-Type: text/plain Date: Thu, 10 Mar 2005 09:37:47 -0800 Message-Id: <1110476267.16432.27.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.0.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2005-03-10 at 14:31 +0000, Mel Gorman wrote: > > > There are 2 kinds of sections: user and kernel. The traditional > > > ZONE_HIGHMEM is full of user sections (except for vmalloc). > > And PTEs if configured to be allocated from high memory. I have not double > checked but I don't think they can be trivially reclaimed. We've run into a couple of these pieces of highmem that can't be reclaimed. The latest one are pages for the new pipe buffers. We could code these up with a flag something like __GFP_HIGHMEM_NORCLM, that is __GFP_HIGHMEM in the normal case, but 0 in the hotplug case (at least for now). > > > Any > > > section which has slab pages or any kernel caller to alloc_pages() is > > > a kernel section. > > Slab pages could be moved to the user section as long as the cache owner > was able to reclaim the slabs on demand. At least for the large consumers of slab (dentry/inode caches), they can't quite reclaim on demand. I was picking Dipankar's brain about this one day, and there are going to be particularly troublesome dentries, like "/", that are going to need some serious rethinking to be able to forcefully free. -- Dave