On 2012-09-18 02:30, Jianpeng Ma wrote: > On 2012-09-18 02:27 Jens Axboe <ax...@kernel.dk> Wrote: >> On 2012-09-17 19:55, Tejun Heo wrote: >>> (cc'ing Jens) >>> >>> On Mon, Sep 17, 2012 at 09:22:28AM -0400, Steven Rostedt wrote: >>>> On Mon, 2012-09-17 at 19:33 +0800, Jianpeng Ma wrote: >>>>> Hi all: >>>>> I used blktrace to trace some io.But i can't find requests merge. I >>>>> searched the code and did't not find. >>>>> Why? >>>>> >>>> >>>> No idea. I don't use blktrace much, but I Cc'd those that understand it >>>> better than I. >> >> Works for me: >> >> [...] >> >> >> 8,0 0 26 0.009147735 664 A WS 315226143 + 8 <- (8,7) >> 19406344 >> 8,0 0 27 0.009148677 664 Q WS 315226143 + 8 >> [btrfs-submit-1] >> 8,0 0 28 0.009152967 664 G WS 315226143 + 8 >> [btrfs-submit-1] >> 8,0 0 29 0.009154242 664 P N [btrfs-submit-1] >> 8,0 0 30 0.009155538 664 A WS 315226151 + 8 <- (8,7) >> 19406352 >> 8,0 0 31 0.009155743 664 Q WS 315226151 + 8 >> [btrfs-submit-1] >> 8,0 0 32 0.009157086 664 M WS 315226151 + 8 >> [btrfs-submit-1] >> 8,0 0 33 0.009158716 664 I WS 315226143 + 16 >> [btrfs-submit-1] >> >> That's from a quick trace of /dev/sda. I started blktrace, then did: >> >> $ dd if=/dev/zero of=foo bs=4k count=128 && sync >> >> to ensure that I knew merges would be happening. Output stats at the end: >> >> Total (sda): >> Reads Queued: 7, 44KiB Writes Queued: 447, >> 7692KiB >> Read Dispatches: 7, 44KiB Write Dispatches: 416, >> 7692KiB >> Reads Requeued: 0 Writes Requeued: 0 >> Reads Completed: 7, 44KiB Writes Completed: 435, >> 5864KiB >> Read Merges: 0, 0KiB Write Merges: 23, >> 428KiB >> IO unplugs: 78 Timer unplugs: 0 >> >> -- >> Jens Axboe >> > First, Thanks your time! > If i understand correctly, the merge of your example is bio with > request, not request wiht request. Yes or no?
It is bio to request, correct. Request to request merges are relatively more rare. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
