From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 27 May 2001 16:06:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 27 May 2001 16:06:05 -0400 Received: from penguin.e-mind.com ([195.223.140.120]:31280 "EHLO penguin.e-mind.com") by vger.kernel.org with ESMTP id ; Sun, 27 May 2001 16:05:46 -0400 Date: Sun, 27 May 2001 22:05:36 +0200 From: Andrea Arcangeli To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Alan Cox , "David S. Miller" , Alexey Kuznetsov , arjanv@redhat.com Subject: Re: [patch] softirq-2.4.5-A1 Message-ID: <20010527220536.B731@athlon.random> In-Reply-To: <20010527191249.I676@athlon.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ; from mingo@elte.hu on Sun, May 27, 2001 at 09:08:51PM +0200 X-GnuPG-Key-URL: http://e-mind.com/~andrea/aa.gnupg.asc X-PGP-Key-URL: http://e-mind.com/~andrea/aa.asc Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 27, 2001 at 09:08:51PM +0200, Ingo Molnar wrote: > i took at look at your ksoftirq stuff yesterday, and i think it's > completely unnecessery and adds serious overhead to softirq handling. The > whole point of softirqs is to have maximum scalability and no > serialization. Why did you add ksoftirqd, would you mind explaining it? The only case ksoftirqd runs is when the stock kernel does the wrong thing and potentially delays the softirq of 1/HZ. Nothing else. When current kernel does the right thing ksoftirq cannot generate any scalability problem and furthmore ksoftirqd is a per-cpu thing so if you face a scalability problem with it that simply means you need to fix the scheduler because then it means you would face a scalability issue as well every time a tux thread calls schedule(). 90% of the time ksoftirqd will never run, when it runs it means you want to pay for a scheduler run to get it running. The price of the scheduler is just the price for the logic that balance the softirq load in a fair manner and without buggy latencies. Andrea