From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 7 Mar 2007 01:39:42 -0800 From: Andrew Morton Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Message-Id: <20070307013942.5c0fadff.akpm@linux-foundation.org> In-Reply-To: <20070307092903.GJ18774@holomorphy.com> References: <20070221023656.6306.246.sendpatchset@linux.site> <20070221023735.6306.83373.sendpatchset@linux.site> <20070306225101.f393632c.akpm@linux-foundation.org> <20070307070853.GB15877@wotan.suse.de> <20070307081948.GA9563@wotan.suse.de> <20070307082755.GA25733@elte.hu> <20070307003520.08b1a082.akpm@linux-foundation.org> <20070307092903.GJ18774@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Bill Irwin Cc: Ingo Molnar , Nick Piggin , Linux Memory Management , Linux Kernel , Benjamin Herrenschmidt , Paolo 'Blaisorblade' Giarrusso List-ID: On Wed, 7 Mar 2007 01:29:03 -0800 Bill Irwin wrote: > On Wed, 7 Mar 2007 09:27:55 +0100 Ingo Molnar wrote: > >> btw., if we decide that nonlinear isnt worth the continuing maintainance > >> pain, we could internally implement/emulate sys_remap_file_pages() via a > >> call to mremap() and essentially deprecate it, without breaking the ABI > >> - and remove all the nonlinear code. (This would split fremap areas into > >> separate vmas) > > On Wed, Mar 07, 2007 at 12:35:20AM -0800, Andrew Morton wrote: > > I'm rather regretting having merged it - I don't think it has been used for > > much. > > Paolo's UML speedup patches might use nonlinear though. > > Guess what major real-life application not only uses nonlinear daily > but would even be very happy to see it extended with non-vma-creating > protections and more? uh-oh. SQL server? > It's not terribly typical for things to be > truncated while remap_file_pages() is doing its work, though it's been > proposed as a method of dynamism. It won't stress remap_file_pages() vs. > truncate() in any meaningful way, though, as userspace will be rather > diligent about clearing in-use data out of the file offset range to be > truncated away anyway, and all that via O_DIRECT. The problem here isn't related to truncate or direct-IO. It's just plain-old MAP_SHARED. nonlinear VMAs are now using the old-style dirty-memory management. msync() is basically a no-op and the code is wildly tricky and pretty much untested. The chances that we broke it are considerable. -- 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