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Date: Fri, 21 Aug 2009 11:36:00 -0400 From: Andrew Gallatin <gallatin@...i.com> To: Neil Horman <nhorman@...driver.com> CC: Bill Fink <billfink@...dspring.com>, Linux Network Developers <netdev@...r.kernel.org>, brice@...i.com Subject: Re: Receive side performance issue with multi-10-GigE and NUMA Neil Horman wrote: > On Fri, Aug 21, 2009 at 12:14:21AM -0400, Bill Fink wrote: >> On Thu, 20 Aug 2009, Neil Horman wrote: >> >>> On Thu, Aug 20, 2009 at 03:50:44AM -0400, Bill Fink wrote: >>> >>>> When I tried an actual nuttcp performance test, even when rate limiting >>>> to just 1 Mbps, I immediately got a kernel oops. I tried to get a >>>> crashdump via kexec/kdump, but the kexec kernel, instead of just >>>> generating a crashdump, fully booted the new kernel, which was >>>> extremely sluggish until I rebooted it through a BIOS re-init, >>>> and never produced a crashdump. I tried this several times and >>>> an immediate kernel oops was always the result (with either a TCP >>>> or UDP test). A ping test of 1000 9000-byte packets with an interval >>>> of 0.001 seconds (which is 72 Mbps for 1 second) on the other hand >>>> worked just fine. >>> The sluggishness is expected, since the kdump kernel operates out of such >>> limited memory. don't know why you booted to a full system rather than did a >>> crash recovery. Don't suppose you got a backtrace did you? >> There was a backtrace on the screen but I didn't have a chance to >> record it. BTW did anyone ever think to print the backtrace in >> reverse (first to some reserved memory and then output to the display) >> so the more interesting parts wouldn't have scrolled off the top of >> the screen? >> > The real solution is to use a console to which the output doesn't scroll off the > screen. Normally people use a serial console they can log, or a RAC card that > they can record. Even on a regular vga monitor in text mode, you can set up the > vt iirc to allow for scrolling. Indeed. Another option when setting up a serial console is not practical is netconsole. I've captured a few panics this way on machines like macs, with no serial port support (at the time). Drew -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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