Seems to me like you don't run blktrace and blkparse appropriately. blktrace stores IO trace in multiple files where each file is associated to a CPU core. However, you force the output of blktrace to redirect into a single file. This make some timing Confusion for blkparse in the next step. You are using live blkparse option (-i -) inappropriately. If you want to run live blkparse, you need to feed it through blktrace pipe. Like: #blktrace -d /dev/sda -o - | blkparse -i - If you want to store trace in a file then parse it offline, you need to use --input option of blkparse. Hope it helps Alireza On Tue, Dec 30, 2014 at 9:23 PM, Phillip Susi <psusi@xxxxxxxxxx> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA512 > > On 12/30/2014 08:53 PM, Alireza Haghdoost wrote: >> Can you please share an example ? How much time backward you >> observed after switch ? > > 8,64 2 606 0.019550771 480 D R 2816 + 128 [kworker/2:1H] > 8,64 2 607 0.019551057 480 R R 2816 + 128 [0] > 8,64 2 608 0.019551151 480 I R 2816 + 128 [kworker/2:1H] > 8,64 2 609 0.019979263 0 D R 2816 + 128 [swapper/2] > 8,64 2 610 0.019980728 0 D R 2944 + 128 [swapper/2] > 8,64 2 611 0.020403185 0 C R 2816 + 128 [0] > 8,64 2 612 0.020416690 0 R R 2944 + 128 [0] > 8,64 2 613 0.020416798 0 I R 2944 + 128 [swapper/2] > 8,64 2 614 0.020420237 480 D R 2944 + 128 [kworker/2:1H] > 8,64 2 615 0.020420511 480 R R 2944 + 128 [0] > 8,80 2 2 0.000000042 27566 G R 0 + 8 [hdparm] > 8,80 2 3 0.000001130 27566 P N [hdparm] > 8,80 2 4 0.000003388 27566 Q R 8 + 8 [hdparm] > 8,80 2 5 0.000004343 27566 M R 8 + 8 [hdparm] > 8,80 2 6 0.000005793 27566 Q R 16 + 8 [hdparm] > 8,80 2 7 0.000005979 27566 M R 16 + 8 [hdparm] > 8,80 2 8 0.000006934 27566 Q R 24 + 8 [hdparm] > 8,80 2 9 0.000007092 27566 M R 24 + 8 [hdparm] > > Come to think of it, in this example it didn't even switch to the > other cpu, just the other device ( though typically when that happens > it seems to also switch the cpu ). > > Here is one that is worse: > > 8,64 1 1026 0.075645831 27565 Q R 7800 + 8 [hdparm] > 8,64 1 1027 0.075646030 27565 M R 7800 + 8 [hdparm] > 8,64 1 1028 0.075646911 27565 Q R 7808 + 8 [hdparm] > 8,64 1 1029 0.075647447 27565 G R 7808 + 8 [hdparm] > 8,80 0 1 0.035128312 27566 Q R 5376 + 8 [hdparm] > 8,80 0 2 0.035130922 27566 G R 5376 + 8 [hdparm] > 8,80 0 3 0.035131724 27566 P N [hdparm] > > Would you like the raw trace file? > > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1 > > iQEcBAEBCgAGBQJUo2wwAAoJENRVrw2cjl5RIooH/juX4p9Cz9XLjYbpLL0HtZhb > JnGw4yaZQEBeqBs5h1LL3A6JZnNHx/yAxMO6LteWr4aQf+nKWUyLD+Yj0jid3n+u > MF4yAwYI7PtJZtRzYpY0YlCorQdX2GKj1ajcX4mCHXrmMr2AXr4Ionyek042Q/Lp > cpJRJUL7OfHHhtpTRTf5Xg36yLo/nK1cIFU0bNz21U3o7jWKRKo7PAmulZymCdN0 > 4FULblVSqiC3iqWPFQC8ScYLxZa0uKnsA73hFB4NbVXVXOoDor2DbgiQoF8gKVWn > MmYlMwf5wfBwuPDTaTcVVLNA7weK6Gs79T71/6FLiJGnpaeedDAQyKvYx3j+5PQ= > =nd6f > -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-btrace" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
