From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [patch 00/47] Sparse irq rework Date: Mon, 4 Oct 2010 08:36:34 +0200 Message-ID: <20101004063634.GA2230@elte.hu> References: <20100930221351.682772535@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:51825 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752408Ab0JDGhB (ORCPT ); Mon, 4 Oct 2010 02:37:01 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Eric W. Biederman" Cc: Thomas Gleixner , LKML , linux-arch@vger.kernel.org, Linus Torvalds , Andrew Morton , x86@kernel.org, Peter Zijlstra , Benjamin Herrenschmidt , Paul Mundt , Russell King , David Woodhouse , Jesse Barnes , Yinghai Lu , Grant Likely * Eric W. Biederman wrote: > Looking at this objectively I see a bitmap sized to the formula > 32*NR_CPUS with NR_CPUS expected to double every 18-24 months. Which > means in a decade our worst case will be 2M not 64k. On a 16 TB box? Noise. > Can we please build this with scalable interfaces so we don't have to > do this again in a couple of years, and so we don't have to have > little machines paying the price for big machines, and so that big > machines aren't hamstrung because of data structures built for little > machines. Bitmaps are rather scalable, we use them all around the place. > Perhaps this just requires using ida instead of a bitmap. Erm, IDA/IDR uses a bitmap ... IDA is a dynamically allocated bitmap - but for something as critical as IRQs i'd rather like to see a preallocated bitmap and platform control over the max (nr_irqs). We dont want to allow crappy drivers to install irq 0x12345678 and blow up the bitmap size to dozens of MB, etc. Bitmaps are simple - and that's a virtue. Thanks, Ingo