[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] weird hvm performance issue.
Thanks for your quick response! (mine was delayed by figuring out oprofile.) On Mon, 29 Jan 2007, Keir Fraser wrote: On 29/1/07 18:08, "Luke S. Crawford" <lsc@xxxxxxxxx> wrote:The CPU usage of qemu-dm correlates with the speed of the scroll; exiting from the xm console does not appear to effect the cpu usage of qemu-dm- it will drop to 1% after several minutes. This kind of thing can be a pain to debug. Perhaps instrument qemu-dm and find out interesting things like how often its select() call returns due to an event on a file descriptor rather than due to hitting the timeout? Okay, I have oprofile installed, and mostly figured out; so opreport without console input: [root@1950-2 ~]# opreport -l /usr/lib64/xen/bin/qemu-dm|head CPU: P4 / Xeon with 2 hyper-threads, speed 3191.87 MHz (estimated)Counted GLOBAL_POWER_EVENTS events (time during which processor is not stopped) with a unit mask of 0x01 (mandatory) count 100000 samples % symbol name 13193 32.7483 main_loop_wait 5787 14.3648 cpu_handle_ioreq 3873 9.6138 DMA_run 1904 4.7262 qemu_get_clock 1683 4.1776 qemu_run_timers 1333 3.3088 qemu_del_timer 985 2.4450 __handle_ioreq with console input: [root@1950-2 ~]# opreport -l /usr/lib64/xen/bin/qemu-dm|head CPU: P4 / Xeon with 2 hyper-threads, speed 3191.87 MHz (estimated)Counted GLOBAL_POWER_EVENTS events (time during which processor is not stopped) with a unit mask of 0x01 (mandatory) count 100000 samples % symbol name 11299 29.0904 main_loop_wait 4944 12.7288 cpu_handle_ioreq 3104 7.9916 DMA_run 1729 4.4515 cpu_physical_memory_rw 1481 3.8130 qemu_get_clock 1431 3.6843 iomem_index 1392 3.5838 qemu_run_timers(those two look about the same; but the slow one, it took a good minute to get to 3000 samples, wheras on the 'with console input' test it took maybe 10 seconds. hm. I need to do more reading on this oprofile in the morning (I don't have remote access to a HVM-capable system from home at this moment) Does the slowness happen if you are using the emulated network device at the same time (i.e., does the event to kick back to normal behaviour have to be a console event)? pinging it doesn't help. (the thing that is triggering this is rsync over the network to the drive) I will re-install with a HVM that is a proper linux box (rather than a systemimager boot floppy) and attempt to re-create the problem with dd or rsync in the morning. I guess something may have crept in when we moved to using qemu's asynchronous block i/o code... It is using rsync to copy several gigabytes of files, so it is certainly excersizing the block I/O _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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