From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 30 Jul 2001 20:33:40 +0100 (BST) From: Mark Hemment Subject: Re: Can reverse VM locks? In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: linux-mm@kvack.org List-ID: On Mon, 30 Jul 2001, Rik van Riel wrote: > OK, I've been looking at the lock order reversal too, > though for different reasons ;) > > On Mon, 2 Jul 2001 markhe@veritas.com wrote: > > On Mon, 2 Jul 2001, Rik van Riel wrote: > > > On Mon, 2 Jul 2001 markhe@veritas.com wrote: > > > > > > > Anyone know of any places where reversing the lock ordering would break? > > Yes, very much true. Now what I wanted to ask about: > do you already have a patch which does this or should > I write a patch which does the lock order reversal ? I did do it, only took a couple of hours, but didn't show any measurable improvement on a four-way box so I put it on the back-burner. It is probably lying around on an off-lined disk somewhere - I'll try to dig it out tomorrow (time for pub/home in the UK), or re-code it. Three points to note; 1) Looked like it might allow for easily coding of per page-cache line spinlocks (if we want to go there). 2) I suspected the pagemap_lru_lock was still under heavy contention (the reversal wouldn't have helped it). 3) In filemap.c, the pagecache_lock and pagemap_lru_lock are far too "close" - need to be L1 cached aligned. Mark -- 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/