From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262386AbTEUVaX (ORCPT ); Wed, 21 May 2003 17:30:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262390AbTEUVaX (ORCPT ); Wed, 21 May 2003 17:30:23 -0400 Received: from fmr02.intel.com ([192.55.52.25]:59094 "EHLO caduceus.fm.intel.com") by vger.kernel.org with ESMTP id S262386AbTEUVaV convert rfc822-to-8bit (ORCPT ); Wed, 21 May 2003 17:30:21 -0400 content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-MimeOLE: Produced By Microsoft Exchange V6.0.6375.0 Subject: RE: userspace irq balancer Date: Wed, 21 May 2003 14:43:18 -0700 Message-ID: <3014AAAC8E0930438FD38EBF6DCEB5640204334F@fmsmsx407.fm.intel.com> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: userspace irq balancer Thread-Index: AcMfpU3dOwtkQrUWQAq6x//iOSX8ZAAJe2KQ From: "Nakajima, Jun" To: Cc: , , , , , X-OriginalArrivalTime: 21 May 2003 21:43:18.0788 (UTC) FILETIME=[FE1C5C40:01C31FE1] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Again, since the userland is using /proc/irq/N/smp_affinity, the in-kernel one won't touch whatever settings done by the userlannd. So I don't think we have issues here - if the userland has more knowledge, then it simply uses binding. If not, use the generic but dumb one in the kernel. Same thing as scheduling. If the dumb one has a critical problem, we should fix it. At the same time, I don't believe a single almighty userland policy exists, either. One might need to write or modify his program to do the best for the system anyway. Or a very simple script might just work fine. Jun > -----Original Message----- > From: James Cleverdon [mailto:jamesclv@us.ibm.com] > Sent: Wednesday, May 21, 2003 7:27 AM > To: David S. Miller; akpm@digeo.com > Cc: arjanv@redhat.com; haveblue@us.ibm.com; wli@holomorphy.com; > pbadari@us.ibm.com; linux-kernel@vger.kernel.org; gh@us.ibm.com; > johnstul@us.ibm.com; mannthey@us.ibm.com > Subject: Re: userspace irq balancer > > On Tuesday 20 May 2003 05:22 pm, David S. Miller wrote: > > From: Andrew Morton > > Date: Tue, 20 May 2003 02:17:12 -0700 > > > > Concerns have been expressed that the /proc interface may be a bit > racy. > > One thing we do need to do is to write a /proc stresstest tool which > > pokes numbers into the /proc files at high rates, run that under traffic > > for a few hours. > > > > This issue is %100 independant of whether policy belongs in the > > kernel or not. Also, the /proc race problem exists and should be > > fixed regardless. > > > > Nobody has tried improving the current balancer. > > > > Policy does not belong in the kernel. I don't care what algorithm > > people decide to use, but such decisions do NOT belong in the kernel. > > You keep saying that, but suppose I want to try HW IRQ balancing using the > TPR > registers. How could I do that from userspace? And if I could, wouldn't > the > benefit of real time IRQ routing be lost? > > It seems to me that only long term interrupt policy can be done from > userland. > Anything that does fast responses to fluctuating load must be inside the > kernel. > > At the moment we don't do any fast IRQ policy. Even the original > irq_balance > only looked for idle CPUs after an interrupt was serviced. However, > suppose > you had a P4 with hyperthreading turned on. If an IRQ is to be delivered > to > the main thread but it is busy and its sibling is idle, why shouldn't we > deliver the interrupt to the idle sibling? They both share the same > caches, > etc, so cache warmth isn't a problem. > > -- > James Cleverdon > IBM xSeries Linux Solutions > {jamesclv(Unix, preferred), cleverdj(Notes)} at us dot ibm dot com > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/