From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 19 May 2005 04:11:16 -0700 From: Andrew Morton Subject: Re: page flags ? Message-Id: <20050519041116.1e3a6d29.akpm@osdl.org> In-Reply-To: <428C6FB9.4060602@shadowen.org> References: <1116450834.26913.1293.camel@dyn318077bld.beaverton.ibm.com> <20050518145644.717afc21.akpm@osdl.org> <1116456143.26913.1303.camel@dyn318077bld.beaverton.ibm.com> <20050518162302.13a13356.akpm@osdl.org> <428C6FB9.4060602@shadowen.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andy Whitcroft Cc: pbadari@us.ibm.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org List-ID: Andy Whitcroft wrote: > > > How many bits are spare now? ZONETABLE_PGSHIFT hurts my brain. > > The short answer is that on 32 bit architectures there are 24 bits > allocated to general page flags, page-flags.h indicates that 21 are > currently assigned so assuming it is accurate there are currently 3 bits > free. Yipes, I didn't realise we were that close. We can reclaim PG_highmem, use page_zone(page)->highmem We can probably reclaim PG_slab We can conceivably reclaim PG_swapcache, although that stuff got ugly. Would dearly love to nuke PG_reserved, but everybody's scared of that ;) PG_uncached is currently ia64-only and could conceivably be moved to bit 32, except there are rumours that arm might want to use it someday. It's a bit irritating that swsusp uses two flags. I don't see any other low-hanging fruit there. -- 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: aart@kvack.org