On Sat, Dec 13, 2014 at 3:23 AM, Stephen Nichols <Stephen.Nichols@xxxxxxx> wrote: > > Hi all, > > When using fio configuration below.. > > [global] > ioengine=libaio > direct=1 > runtime=600 > bs=32k > iodepth=8 > rw=randrw > rwmixread=80 > percentage_random=100,0 > > [drive1] > filename=/dev/sda > > > I am expecting to see 80% reads, 20% writes where all reads are random and all writes are sequential. I captured a bus trace of traffic to the disk and the bus trace reflected as much with one issue. The write commands are essentially random. Each write begins at a new random LBA. If 2 or more writes occur in a row, the LBA's are sequential based on the block size BUT I feel the heart of this feature would be to emulate a large file write during random access. With that in mind would it be possible for sequential reads or writes within mixed sequential/random workload to remember the last LBA accessed? In this scenario the writes would still only take up 20% of the workload but when a write did occur it should be the next sequential step from the last write. > > > Snippet from the bus trace for reference > > Command LBA > Read FPDMA Queued: 19F3F818 > Read FPDMA Queued: 1CBE2740 > Write FPDMA Queued: 24E35198 > Write FPDMA Queued: 24E351A0 > Read FPDMA Queued: 115A9E10 > Write FPDMA Queued: A3C1968 > Read FPDMA Queued: 20B89488 > Write FPDMA Queued: 336EE0D0 > Write FPDMA Queued: 336EE0D8 > > The problem is that, with non-trivial percentage_random, fio generates next sequential offset off the file's last position, but the latter is global, not per data direction. As a result, with the workload above, one gets the pattern where next write is sequential with respect to the last I/O, not the last write as, I believe, the expectation goes. I've added a debug printout for the last_pos to illustrate the point in the debug output below. ddir=1 are writes. Regards, Andrey fio: set debug option io io 5299 load ioengine libaio drive1: (g=0): rw=randrw, bs=32K-32K/32K-32K/32K-32K, ioengine=libaio, iodepth=8 fio-2.1.14-45-g7003 Starting 1 process io 5301 invalidate cache /tmp/drive1: 0/1048576 io 5301 get_next_block: last pos 0 io 5301 fill_io_u: io_u 0x121ec00: off=32768/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121ec00: off=32768/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121ec00)=0 io 5301 queue: io_u 0x121ec00: off=32768/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 1 io 5301 get_next_block: last pos 65536 io 5301 fill_io_u: io_u 0x121e900: off=753664/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121e900: off=753664/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121e900)=0 io 5301 queue: io_u 0x121e900: off=753664/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 2 io 5301 get_next_block: last pos 786432 io 5301 fill_io_u: io_u 0x121e1c0: off=851968/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121e1c0: off=851968/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121e1c0)=0 io 5301 queue: io_u 0x121e1c0: off=851968/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 3 ================================================================ io 5301 get_next_block: last pos 884736 io 5301 fill_io_u: io_u 0x121dec0: off=884736/len=32768/ddir=1//tmp/drive1 io 5301 prep: io_u 0x121dec0: off=884736/len=32768/ddir=1//tmp/drive1 io 5301 ->prep(0x121dec0)=0 io 5301 queue: io_u 0x121dec0: off=884736/len=32768/ddir=1//tmp/drive1 io 5301 calling ->commit(), depth 4 io 5301 get_next_block: last pos 917504 io 5301 fill_io_u: io_u 0x121dbc0: off=491520/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121dbc0: off=491520/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121dbc0)=0 io 5301 queue: io_u 0x121dbc0: off=491520/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 5 io 5301 get_next_block: last pos 524288 io 5301 fill_io_u: io_u 0x121d8c0: off=393216/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121d8c0: off=393216/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121d8c0)=0 io 5301 queue: io_u 0x121d8c0: off=393216/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 6 io 5301 get_next_block: last pos 425984 io 5301 fill_io_u: io_u 0x121d600: off=0/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121d600: off=0/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121d600)=0 io 5301 queue: io_u 0x121d600: off=0/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 7 io 5301 get_next_block: last pos 32768 io 5301 fill_io_u: io_u 0x121d300: off=65536/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121d300: off=65536/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121d300)=0 io 5301 queue: io_u 0x121d300: off=65536/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 8 io 5301 io_u_queued_completed: min=1 io 5301 getevents: 1 io 5301 io complete: io_u 0x121ec00: off=32768/len=32768/ddir=0//tmp/drive1 io 5301 get_next_block: last pos 98304 io 5301 fill_io_u: io_u 0x121ec00: off=360448/len=32768/ddir=0//tmp/drive1 io 5301 prep: io_u 0x121ec00: off=360448/len=32768/ddir=0//tmp/drive1 io 5301 ->prep(0x121ec00)=0 io 5301 queue: io_u 0x121ec00: off=360448/len=32768/ddir=0//tmp/drive1 io 5301 calling ->commit(), depth 8 io 5301 io_u_queued_completed: min=1 io 5301 getevents: 1 io 5301 io complete: io_u 0x121e900: off=753664/len=32768/ddir=0//tmp/drive1 ================================================================== io 5301 get_next_block: last pos 393216 io 5301 fill_io_u: io_u 0x121e900: off=393216/len=32768/ddir=1//tmp/drive1 io 5301 prep: io_u 0x121e900: off=393216/len=32768/ddir=1//tmp/drive1 io 5301 ->prep(0x121e900)=0 Regards, Andrey > > Let me know what you think, this feature may be working as intended but it seemed off to me. > > Thanks, > Stephen "Nick" Nichols > Western Digital > Enterprise Test Development > > -- > 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 -- 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
