From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikita Danilov MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17036.42124.398130.730456@gargle.gargle.HOWL> Date: Thu, 19 May 2005 18:37:00 +0400 Subject: Re: page flags ? In-Reply-To: <20050519041116.1e3a6d29.akpm@osdl.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> <20050519041116.1e3a6d29.akpm@osdl.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: pbadari@us.ibm.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org List-ID: Andrew Morton writes: > 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. Things like PG_uptodate and PG_error can be moved to the radix-tree tags after checking that they are used only for pages in the mapping, which seems to be the case. > -- Nikita. -- 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