From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 20 Feb 2003 14:19:39 -0300 (BRT) From: Rik van Riel Subject: Re: [PATCH 2.5.62] Partial object-based rmap implementation In-Reply-To: <8390000.1045757611@baldur.austin.ibm.com> Message-ID: References: <8390000.1045757611@baldur.austin.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Content-ID: Content-Disposition: INLINE Sender: owner-linux-mm@kvack.org Return-Path: To: Dave McCracken Cc: Linux Memory Management List-ID: On Thu, 20 Feb 2003, Dave McCracken wrote: > There's been a fair amount of discussion about the advantages of doing > object-based rmap. Unfortunately, not nearly as much about the disadvantages. There are big advantages and disadvantages to both ways of doing reverse mappings. I'm planning to write about both for my OLS paper and analise the algorithmic complexities in more detail so we've got a better idea of exactly what we're facing. > I've been looking into it, and we have the pieces to > do it for file-backed objects, ie the ones that have a real > address_space object pointed to from struct page. The stumbling block > has always been anonymous pages. And algorithmic complexities, for some reason those always seem to be about as unexpected as the Spanish Inquisition. ;) > At Martin Bligh's suggestion, I coded up an object-based implementation for > non-anon pages while leaving the pte_chain code intact for anon pages. My > fork/exit microbenchmark shows roughly 50% improvement for tasks that are > composes of file-backed and/or shared pages. This is the code that Martin > included in 2.5.62-mjb2 and reported his performance results on. But how is performance under memory pressure ? > Anyway, here's the patch if anyone wants to check it out. It's nice, but we'll want to find a way to alleviate some of the worst case complexities. Definately something worth exploring further. It would be good to discuss the pitfalls of object based reverse mapping with Ben LaHaise and Dave Miller, who have implemented such schemes in the past. kind regards, Rik -- Engineers don't grow up, they grow sideways. http://www.surriel.com/ http://kernelnewbies.org/ -- 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