On Mon, Feb 18, 2013 at 2:04 AM, Jens Axboe <axboe@xxxxxxxxx> wrote: > > On Sat, Feb 16 2013, Alireza Haghdoost wrote: > > Hello, > > > > I am using fio to generate a simple sequential workload with request > > size of 128K with following job file but I can observe the generated > > IO request size is 4K, I was wondering who is responsible in block > > layer to shrink the fio requests granularity from 128K to 4K ? : > > > > > > 1 ; -- start job file -- > > 2 [global] > > 3 rw=write > > 4 size=128M > > 5 > > 6 [job1] > > 7 ioengine=libaio > > 8 iodepth=512 > > 9 bs=128k > > 10 direct=1 > > 11 numjobs=1 > > 12 filename=/dev/sde > > 13 ; -- end job file -- > > > > > > The blktrace shows that the request sizes are all 4KB (8 sector), here > > is a peace of output trace that collected while fio is running. > > > > 21 8,64 5 21 0.000031322 29848 I W 32 + 8 [fio] > > 22 8,64 5 22 0.000031868 29848 Q WS 40 + 8 [fio] > > 23 8,64 5 23 0.000032181 29848 G WS 40 + 8 [fio] > > 24 8,64 5 24 0.000032352 29848 I W 40 + 8 [fio] > > 25 8,64 5 25 0.000032826 29848 Q WS 48 + 8 [fio] > > 26 8,64 5 26 0.000033145 29848 G WS 48 + 8 [fio] > > 27 8,64 5 27 0.000033310 29848 I W 48 + 8 [fio] > > 28 8,64 5 28 0.000033781 29848 Q WS 56 + 8 [fio] > > 29 8,64 5 29 0.000034045 29848 G WS 56 + 8 [fio] > > 30 8,64 5 30 0.000034227 29848 I W 56 + 8 [fio] > > 31 8,64 5 31 0.000034498 29848 D W 32 + 8 [fio] > > 32 8,64 5 32 0.000036314 29848 D W 40 + 8 [fio] > > 33 8,64 5 33 0.000038032 29848 D W 48 + 8 [fio] > > What kernel are you using? For a proper setup, the above fio job should > go down to the hardware as 128KB sized requests. Depending on the kernel > and driver, there might be timing issues that cause it to not get > properly coalesced in the scheduler, however. > > -- > Jens Axboe > Jens, Thanks for your replay. I am using Ubuntu server 10.10 kernel version 2.6.35-22-server. /dev/sde is a NAS drive. NIC card adapter is QLogic Fiber Channel and we are using qla2xxx driver. I believe somewhere in block layer interface 128KB request converts to 8KB requests. I am using noop IO scheduler with queue size (nr_request) of 2048 and nomerge value 2. I really appreciate your further input. Thanks Alireza -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
