Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 13 Oct 2002 02:56:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 13 Oct 2002 02:56:05 -0400 Received: from smtp801.mail.sc5.yahoo.com ([66.163.168.180]:30767 "HELO smtp801.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id ; Sun, 13 Oct 2002 02:56:02 -0400 From: "Joseph D. Wagner" To: "'Rob Mueller'" , "'Mark Hahn'" Cc: , "'Jeremy Howard'" Subject: RE: Strange load spikes on 2.4.19 kernel Date: Sun, 13 Oct 2002 02:01:44 -0500 Message-ID: <000001c27286$6ab6bc60$7443f4d1@joe> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4024 In-Reply-To: <113001c27282$93955eb0$1900a8c0@lifebook> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Importance: Normal Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3078 Lines: 80 I'll let you in on a dirty little secret. The Linux file system does not utilize SMP. That's right. All file processes go through one and only one processor. It has to do with the fact that the Linux kernel is a non-preemptive kernel. Linus, in his infinite wisdom, made a "strategiery" decision that it would be better for one process to be able to grind your machine to a halt than to redo and rework sections of the kernel that don't allow for preemption. Try switching kernels to the Linux Kernel Preemption Project: http://sourceforge.net/projects/kpreempt -----Original Message----- From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Rob Mueller Sent: Sunday, October 13, 2002 1:34 AM To: Mark Hahn Cc: linux-kernel@vger.kernel.org; Jeremy Howard Subject: Re: Strange load spikes on 2.4.19 kernel We've just discovered that this is actually happening on another one of our machines as well. This machine uses 2.4.18 kernel, ext3 and has 2 SCSI drives and 2 IDE drives which hold the main user mailbox data. Also it's a P3 with a completely different motherboard rather than an Athlon, so it doesn't seem to be hardware related in that respect. > well, it's conceivable that if something is blocking a bunch > of procs, it would also block your shell and ps, so not show up. > "vmstat 1" might work better, though it's munging plenty of > /proc files so is hardly immune to that. But the ps/shell would only use CPU time, and there's plenty of that available. Unless it was something everything would block on... what could that be? A spin lock or something? Some interrupt routine? Would that even result in other processes being counted as blocked process? Also Let me do a calculation, though I have no idea if this is right or not... a) the first item in the uptime output is 'system load average for the last 1 minute' b) it seems to only update/recalculate every 5 seconds c) it jumps from < 1 to 20 in 1 interval (eg 5 seconds) This means that for it to jump from < 1 to 20 in 5 seconds, there must be on average about 60/5 * 20 = 240 processes blocked over those 5 seconds waiting for run time of some sort for the load to jump 20 points. Is that right? > but it's worth asking: do you notice a hiccup other than by looking > at the loadav? that is, suppose the loadav is simply miscalculated... Well yes, there definitely does seem to be a performance hit on the whole system when the load jumps, everything feels significantly more 'sluggish' during the spikes is the best I can describe it right now... Rob - 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/ - 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/