From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mario Smarduch Date: Thu, 13 Mar 2003 20:44:27 +0000 Subject: Re: [Linux-ia64] page size > 16KB Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org David Mosberger wrote: > >>>>> On Wed, 12 Mar 2003 13:51:16 -0600, Mario Smarduch said: > > Mario> Hi David, I'm very curious about your statement regarding > Mario> reproducible results - a desirable attribute for many > Mario> applications in our case soft real-time predictability. With > Mario> the caches on Itanium2 being highly associative, did you > Mario> notice a dramatic change in reproducibility as you did in TLB > Mario> efficiency? This is assuming a locked memory intensive > Mario> application or this was too long ago for you to remember :) > > Heh, I barely remember what I ate for dinner last night, so I > certainly don't remember what that application was about... ;-) > > Apps with large arrays certainly can see significant variation due to > lack of page coloring in the kernel, even with high associativity. I > ran a Monte Carlo simulation on this a while ago and attached the > results below. > > As you can see, high associativity keeps page-coloring effects away up > until you occupy about 1.5-2MB (out of a 3MB cache). So if you have, > say, a 3MB array, you'd clearly expect to see page-coloring effects. David, thanks for pulling this up - its very interesting. For 12-way associtivity 64KB pg size does stand out quite a bit from 4,8,16KB, although the effect appears to be more visual because 32KB is not supported. > > > The graph also shows that larger page sizes somewhat reduce the > negative effets of lack of page-coloring (not entirely intuitive, but > it's pretty complex as to what's going on, so it's not surprising that > intuition doesn't get us very far). yes its a very painful graph to look at :) - Mario. > > > I should update the graph for Madison some day. > > --david > > ------------------------------------------------------------------------ > Name: coll.pdf > coll.pdf Type: Portable Document Format (application/pdf) > Encoding: base64 > Description: coll.pdf