Hi My windows pv driver''s read performance is acceptable but write performance is bad and worse then QEMU mode. I use DebugView to get some debug information from drivers. I found something strange but interesting. I use IoMeter to test a 2GB disk which formatted as NTFS file system. Set VCPU = 1, Memory = 600MB. All test are done on the same test machine. Here are some log brief, I just print one command work process for an example, the other commands in log files show the same result. Windows Server 2008 X64, 32K, 100% sequence Read -Log No.- - Time- - Log- 00003944 1.28332651 XenVBD: Srb FFFFFA8000E82F90, startLBA 1912736, blockCount 64, offset 0 00003945 1.28334212 XenVBD: Device FFFFFA8000A67008, Notify event channel 5 00003946 1.28373182 XenPCI: send software interrupt to event channel 5 00003947 1.28375566 XenVBD: ISR StartLBA:1912736, blockCount:64 [Response time = 1.28373182 - 1.28334212 0.0003897 ] Windows Server 2008 X64, 32K, 100% sequence Write -Log No.- - Time- - Log- 00002718 5.05471611 XenVBD: Srb FFFFFA8000E82F90, startLBA 1892896, blockCount 64, offset 0 00002719 5.05474854 XenVBD: Device FFFFFA8000A67008, Notify event channel 5 00002720 5.05863619 XenPCI: send software interrupt to event channel 5 00002721 5.05865955 XenVBD: ISR StartLBA:1892896, blockCount:64 [Response time = 5.05863619 - 5.05474854 = 0.00388765 ] For each log segment, line 1 means xenvbd driver get an SCSI command from system upper driver (such as file system), line 2 means xenvbd driver finish SCSI command analyzing, fill it to a ring buffer and notify the event channel to tell backend driver that a command is ok and need backend to deal with. line 3 means xenpci driver get an event channel notify from backend and send a software interrupt to tell xenvbd driver that a command is finished. line 4 means xenvbd driver get a interrupt from xenpci driver. ISR is called to complete a SCSI command. What I found is X64 32K Write command takes a long time to get response from backend. Response time from set notify to event channel to get event notify from event channel is longer then Read command (about 10 times). I know a hard disk drive will take more time to deal with a Write command then Read command, but I don''t think it will be 10 times. So any one can tell me why backend driver need so much time to deal with a 32K Write command from a X64 windows PV HVM? Can I set some parameter to get some log from backend or something else? I use xen 3.1 series. Any feedback is appreciate. thanks wayne _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel