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?
Thanks! Jianpeng
