Date: Wed, 10 Nov 2004 10:40:44 +0100 From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@DeepCore.dk> To: Robert Watson <rwatson@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: 5.3-RELEASE: WARNING - WRITE_DMA interrupt timout - what does it mean? Message-ID: <4191E21C.5040307@DeepCore.dk> In-Reply-To: <Pine.NEB.3.96L.1041110091049.60848T-100000@fledge.watson.org> References: <Pine.NEB.3.96L.1041110091049.60848T-100000@fledge.watson.org>
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Robert Watson wrote: >>It means that the disk has processed the write request (interrupt seen)= , >>but that the system (the bio_taskqueue) hasn't been able to get the >>result returned to the kernel.=20 >> >>Your disk is not involved in this problem since it has done its part, >>but the rest of the system is either busy with something else, or there= >>are bugs lurking that prohibits the bio_taskqueue from running.=20 >> >>Either way its a WARNING not a FAILURE :)=20 >=20 >=20 > I'm still a bit skeptical that the task queue is at fault -- I run my > notebook with continuous measurement of the latency to schedule tasks, > generating a warning for any latency > .5 seconds, and the only time I > ever see that sort of latency is during the boot process when ACPI has > scheduled a task to run, but the task queue thread has not yet been > allowed to run: Right, the timeout is 5 secs. I havn't looked into how the taskqueues=20 are handled recently, but in case of ATA read/writes it is the=20 bio_taskqueue handled by geom thats in use not the catchall ones, does=20 your timing cover that as well? There are several explanations for what happens: 1. the bio_taskqueue is not pushing requests through. 2. the disks takes long to respond and uses almost all of the 5 secs 3. timeouts are not working and fireing at random. I cannot reproduce the symptoms on any of my HW no matter how hard I hit = it, and I dont really belive in items 2 and 3 above, however I've been=20 proven wrong before :) --=20 -S=F8ren
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