Re: last_block() vs. min_bs when > blockalign

[Jens Axboe <axboe@kernel.dk>]

Thanks, applied.


On 01/27/2015 03:42 PM, Justin Eno (jeno) wrote:
> The attached updated patch produces the desired behavior.  If min_bs is larger than blockalign, last_block() now returns a suitable value.
>
> Thanks,
> Justin
>
> -----Original Message-----
> From: Justin Eno (jeno)
> Sent: Tuesday, January 27, 2015 1:35 PM
> To: 'fio@vger.kernel.org'
> Subject: RE: last_block() vs. min_bs when > blockalign
>
> Please disregard the patch - it incorrectly limits the target write range.  I will work on a proper fix.  Sorry for the noise.
>
> -Justin
>
> -----Original Message-----
> From: Justin Eno (jeno)
> Sent: Tuesday, January 27, 2015 12:00 PM
> To: 'fio@vger.kernel.org'
> Subject: last_block() vs. min_bs when > blockalign
>
> Hi Jens and all,
>
> I have found that when performing mixed-sized random writes, fio ceases writing early due to last_block() not respecting min_bs.
> The attached workload demonstrates the issue.  When run with io debugging enabled, "failed getting buflen" is reported, and the written data falls short of the total requested (in this case, 10M), e.g., ###############################################
> [jeno@rhel fio-clean]$ ./fio --debug=io examples/random-fill.fio
> fio: Any use of blockalign= turns off randommap
> fio: set debug option io
> io       25214 load ioengine sync
> write-phase: (g=0): rw=randwrite, bs=1K-5K/1K-5K/1K-5K, ioengine=sync, iodepth=1 fio-2.2.5-3-g209e Starting 1 thread
> write-phase: Laying out IO file(s) (1 file(s) / 5MB)
> io       25214 invalidate cache datafile.tmp: 0/5242880
> io       25214 invalidate cache datafile.tmp: 0/5242880
> io       25214 fill_io_u: io_u 0x7fe49c003d40: off=315904/len=1024/ddir=1/datafile.tmp
> io       25214 prep: io_u 0x7fe49c003d40: off=315904/len=1024/ddir=1/datafile.tmp
> io       25214 ->prep(0x7fe49c003d40)=0
> io       25214 queue: io_u 0x7fe49c003d40: off=315904/len=1024/ddir=1/datafile.tmp
> io       25214 io complete: io_u 0x7fe49c003d40: off=315904/len=1024/ddir=1/datafile.tmp
> ...
> io       25214 fill_io_u: io_u 0x7fe49c003d40: off=4930560/len=5120/ddir=1/datafile.tmp
> io       25214 prep: io_u 0x7fe49c003d40: off=4930560/len=5120/ddir=1/datafile.tmp
> io       25214 ->prep(0x7fe49c003d40)=0
> io       25214 queue: io_u 0x7fe49c003d40: off=4930560/len=5120/ddir=1/datafile.tmp
> io       25214 io complete: io_u 0x7fe49c003d40: off=4930560/len=5120/ddir=1/datafile.tmp
> io       25214 io_u 0x7fe49c003d40, failed getting buflen
> io       25214 io_u 0x7fe49c003d40, setting file failed
> io       25214 get_io_u failed
> io       25214 close ioengine sync
> io       25214 free ioengine sync
>
> write-phase: (groupid=0, jobs=1): err= 0: pid=25281: Tue Jan 27 10:33:50 2015
>    write: io=4335.0KB, bw=585007B/s, iops=195, runt=  7588msec
>      clat (usec): min=762, max=17788, avg=5100.38, stdev=2509.05
>       lat (usec): min=764, max=17790, avg=5101.80, stdev=2509.06
>      clat percentiles (usec):
>       |  1.00th=[  868],  5.00th=[ 1240], 10.00th=[ 1704], 20.00th=[ 2544],
>       | 30.00th=[ 3440], 40.00th=[ 4192], 50.00th=[ 5024], 60.00th=[ 5984],
>       | 70.00th=[ 6752], 80.00th=[ 7648], 90.00th=[ 8384], 95.00th=[ 8896],
>       | 99.00th=[ 9280], 99.50th=[10304], 99.90th=[17792], 99.95th=[17792],
>       | 99.99th=[17792]
>      bw (KB  /s): min=  520, max=  640, per=99.98%, avg=570.87, stdev=35.30
>      lat (usec) : 1000=2.76%
>      lat (msec) : 2=11.25%, 4=22.76%, 10=62.63%, 20=0.61%
>    cpu          : usr=0.12%, sys=0.28%, ctx=1486, majf=0, minf=1
>    IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
>       submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
>       complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
>       issued    : total=r=0/w=1485/d=0, short=r=0/w=0/d=0, drop=r=0/w=0/d=0
>       latency   : target=0, window=0, percentile=100.00%, depth=1
>
> Run status group 0 (all jobs):
>    WRITE: io=4335KB, aggrb=571KB/s, minb=571KB/s, maxb=571KB/s, mint=7588msec, maxt=7588msec ...
> ###############################################
>
> The attached patch changes last_block() to respect min_bs.
>
> Thanks,
> Justin
>


-- 
Jens Axboe