There's no obvious reason for this. Unless you are encountering some sort of error during your transfers, causing some of the operations to be retried? If there were any errors, they would should up in the log when you turn on CONFIG_USB_STORAGE_DEBUG.
No errors at all when running "normal" kernel. As for CONFIG_USB_DEBUG and CONFIG_USB_STORAGE_DEBUG enabled kernel, please see dmesg output below.
Vit --- dmesg output --- usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 2a 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2658 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2658 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 68 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2659 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2659 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 7d 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x265a L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x265a R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 a7 49 00 00 04 00 usb-storage: Bulk Command S 0x43425355 T 0x265b L 2048 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 2048 bytes, 1 entries usb-storage: Status code 0; transferred 2048/2048 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x265b R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 2a 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x265c L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x265c R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 68 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x265d L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x265d R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 2a 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x265e L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x265e R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 68 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x265f L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x265f R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 7d 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2660 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2660 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 a7 4d 00 00 04 00 usb-storage: Bulk Command S 0x43425355 T 0x2661 L 2048 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 2048 bytes, 1 entries usb-storage: Status code 0; transferred 2048/2048 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2661 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 2a 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2662 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2662 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 68 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2663 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2663 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 2a 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2664 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2664 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 68 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2665 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2665 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 00 7d 00 00 01 00 usb-storage: Bulk Command S 0x43425355 T 0x2666 L 512 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 512 bytes, 1 entries usb-storage: Status code 0; transferred 512/512 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2666 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. usb-storage: queuecommand called usb-storage: *** thread awakened. usb-storage: Command WRITE_10 (10 bytes) usb-storage: 2a 00 00 00 a7 51 00 00 04 00 usb-storage: Bulk Command S 0x43425355 T 0x2667 L 2048 F 0 Trg 0 LUN 0 CL 10 usb-storage: usb_stor_bulk_transfer_buf: xfer 31 bytes usb-storage: Status code 0; transferred 31/31 usb-storage: -- transfer complete usb-storage: Bulk command transfer result=0 usb-storage: usb_stor_bulk_transfer_sglist: xfer 2048 bytes, 1 entries usb-storage: Status code 0; transferred 2048/2048 usb-storage: -- transfer complete usb-storage: Bulk data transfer result 0x0 usb-storage: Attempting to get CSW... usb-storage: usb_stor_bulk_transfer_buf: xfer 13 bytes usb-storage: Status code 0; transferred 13/13 usb-storage: -- transfer complete usb-storage: Bulk status result = 0 usb-storage: Bulk Status S 0x53425355 T 0x2667 R 0 Stat 0x0 usb-storage: scsi cmd done, result=0x0 usb-storage: *** thread sleeping. ------------------------------------------------------- This SF.Net email is sponsored by the 'Do More With Dual!' webinar happening July 14 at 8am PDT/11am EDT. 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