From mboxrd@z Thu Jan 1 00:00:00 1970 From: Blaisorblade Subject: Re: [patch 00/14] remap_file_pages protection support Date: Wed, 3 May 2006 02:25:49 +0200 References: <20060430172953.409399000@zion.home.lan> <4456D5ED.2040202@yahoo.com.au> In-Reply-To: <4456D5ED.2040202@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200605030225.54598.blaisorblade@yahoo.it> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andrew Morton , linux-kernel@vger.kernel.org, Linux Memory Management , Ulrich Drepper , Val Henson List-ID: On Tuesday 02 May 2006 05:45, Nick Piggin wrote: > blaisorblade@yahoo.it wrote: > > This will be useful since the VMA lookup at fault time can be a > > bottleneck for some programs (I've received a report about this from > > Ulrich Drepper and I've been told that also Val Henson from Intel is > > interested about this). I guess that since we use RB-trees, the slowness > > is also due to the poor cache locality of RB-trees (since RB nodes are > > within VMAs but aren't accessed together with their content), compared > > for instance with radix trees where the lookup has high cache locality > > (but they have however space usage problems, possibly bigger, on 64-bit > > machines). > Let's try get back to the good old days when people actually reported > their bugs (togther will *real* numbers) to the mailing lists. That way, > everybody gets to think about and discuss the problem. I've not seen the numbers indeed, I've been told of a problem with a "customer program" and Ingo connected my work with this problem. Frankly, I've been always astonished about how looking up a 10-level tree can be slow. Poor cache locality is the only thing that I could think about. That said, it was an add-on, not the original motivation of the work. -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com -- 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