From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 15 Feb 2007 19:18:58 -0800 From: Andrew Morton Subject: Re: [RFC] Remove unswappable anonymous pages off the LRU Message-Id: <20070215191858.1a864874.akpm@linux-foundation.org> In-Reply-To: References: <20070215171355.67c7e8b4.akpm@linux-foundation.org> <45D50B79.5080002@mbligh.org> <20070215174957.f1fb8711.akpm@linux-foundation.org> <20070215184800.e2820947.akpm@linux-foundation.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: Christoph Lameter Cc: Martin Bligh , linux-mm@kvack.org, Nick Piggin , Peter Zijlstra , KAMEZAWA Hiroyuki , Rik van Riel List-ID: On Thu, 15 Feb 2007 18:50:39 -0800 (PST) Christoph Lameter wrote: > On Thu, 15 Feb 2007, Andrew Morton wrote: > > > We discussed that a while back and iirc ia64 has gone and gobbled most of > > the upper 32bits. Someone went and added some ascii art around the > > PG_uncached definition but it is incomprehensible. It seems to claim that > > ia64 has gone and used all 32 bits, dammit. If so, some adjustments to > > ia64 might be called for. > > Yes ia64 has used the upper 32 bit. However, the lower 32 bits are fully > usable. So we have 32-20 = 12 bits to play with on 64 bit. OK. But not many things are 64-bit-only? > > > > > page_type = { SLAB, LRU, MLOCK, RESERVED, BUDDY, } > > > > Yeah, maybe. There doesn't seem to be a lot of room for that though - a > > lot of those flags are quite independent and can occur simultaneously. > > None of the above can occur simultaneously. OK. The actual implementation details might get messy though. We can do a non-atomic rmw of the three bits but that could corrupt a concurrent modification of a different flag. Or we could do a succession of three set_bit/clear_bit operations, but that exposes intermediate invalid states. It can be done I guess, but it'd be fiddly. -- 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