Date: Fri, 07 Nov 2003 00:45:47 -0700 From: Scott Long <scottl@freebsd.org> To: Kevin Oberman <oberman@es.net> Cc: current@freebsd.org Subject: Re: Kernel memory leak in ATAPI/CAM or ATAng? Message-ID: <3FAB4DAB.5060901@freebsd.org> In-Reply-To: <20031106235641.7F5555D07@ptavv.es.net> References: <20031106235641.7F5555D07@ptavv.es.net>
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Kevin Oberman wrote: >>Date: Thu, 6 Nov 2003 11:23:30 -0500 (EST) >>From: Robert Watson <rwatson@freebsd.org> >> >> >>On Thu, 6 Nov 2003, Kevin Oberman wrote: >> >> >>>I have learned a bit more about the problems I have been having with >>>the DVD drive on my T30 laptop. When I have run the drive for an >>>extended time (like 2 or 3 hours), I invariably have my system lock up >>>because it can't malloc kernel memory for the ATAPI/CAM or ATA >>>device. (Usually it's both.) >>> >>>The only recovery seems to be to reboot the system. >> >>Is it possible to drop to DDB and generate a coredump at that point? If >>so, you can run vmstat on the core to look at memory use statistics in a >>post-mortem way. As to what to look for: "big numbers" is about the limit >>of what I can suggest, I'm afraid :-). Usually the activity of choice is >>to compare vmstat statistics (with -m and -z) during normal operation and >>when the leak has occurred, and look for any marked differences. It's >>worth observing that there are two failure modes here that appear almost >>identical: (1) a memory leak resulting in address space exhaustion for the >>kernel, and (2) a tunable maximum allocation being too high for the >>available address space. Note that (2) isn't a leak, simply a poorly >>tuned value. We've noticed a number of tuned memory limits were set when >>memory sizes on systems were much lower, and so we've had to readjust the >>tuning parameters for large memory systems. Likewise, a number of >>problems were observed when PAE was introduced, as some of the tuning >>parameters scaled with the amount of physical memory, not with the >>addressable space for the kernel. So we probably want to be on the look >>out for both of these possibilities. > > > Well, I have no details to this point, but 'vmstat -m' makes the > problem obvious. The amount of kernel memory allocated to ATA request > climbs forever and after enough data is transferred, it runs out of > KVM. This is a continual leak, and monitoring it on the running system > makes it pretty clear that something is leaking. I don't think (2) is > the issue. Because the field allocated in vmstat are not large enough, > this is a bit hard to read. The field all merge into some REALLY large > numbers. After reboot, it is <5K. When running mencode I see this > increasing at a rate of a bit under 1.9 MB per minute. > > It does not look like a tuning issue. No matter how big KVM is allowed > to grow, it's only a matter of time until it is gone. > > I am going to do some testing to see what operations seem to causse > this. I assume it does not happen all of the time or everyone would > have seen it. I suspect it only happens with ATAPI/CAM activity, > possibly only with simultaneous ATA and ATAPI/COM activity. Does vmstat -m show which malloc type is growing? Knowing this will greatly speed up the debugging process. Thanks! Scott
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