From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 30 May 2006 10:02:24 -0700 (PDT) From: Christoph Lameter Subject: Re: [PATCH 1/3] mm: tracking shared dirty pages In-Reply-To: <7966.1149006374@warthog.cambridge.redhat.com> Message-ID: References: <20060525135534.20941.91650.sendpatchset@lappy> <20060525135555.20941.36612.sendpatchset@lappy> <24747.1148653985@warthog.cambridge.redhat.com> <12042.1148976035@warthog.cambridge.redhat.com> <7966.1149006374@warthog.cambridge.redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: David Howells Cc: Peter Zijlstra , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Andrew Morton , Christoph Lameter , Martin Bligh , Nick Piggin , Linus Torvalds List-ID: On Tue, 30 May 2006, David Howells wrote: > > If set_page_dirty cannot reserve the page then we know that some severe > > action is required. The FS method set_page_dirty() could: > > But by the time set_page_dirty() is called, it's too late as the code > currently stands. We've already marked the PTE writable and dirty. The > page_mkwrite() op is called _first_. We are in set_page_dirty and this would be part of set_page_dirty processing. > > 2. Track down all processes that use the mapping (or maybe less > > That's bad, even if you restrict it to those that have MAP_SHARED and > PROT_WRITE set. They should not be terminated if they haven't attempted to > write to the mapping. Its bad but the out of space situation is an exceptional situation. We do similar contortions when we run out of memory space. As I said: One can track down the processes that have dirtied the pte to the page in question and just terminate those and remove the page. > What's wrong with my suggestion anyway? Adds yet another method with functionality that for the most part is the same as set_page_dirty(). The advantage of such a method seems to be that it reserves filesystem space for pages that could potentially be written to. This allows the filesystem to accurately deal with out of space situations (a very rare condition. Is this really justifiable?). Maybe having already reserved space could speed up the real dirtying of pages? -- 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