Re: Repeat given pattern with buffer_compress_percentage

[Jens Axboe <axboe@kernel.dk>]

On 12/05/2014 10:02 AM, Jens Axboe wrote:
> On 12/05/2014 12:25 AM, Karthick Srinivasachary wrote:
>> Hi Jens,
>>
>> Awesome.. Thanks for the fix..!
>> With compress_percentage 80 or more, fio verify is failing. I don't
>> think there any issue with storage in my test environment. Do you
>> think we have a bug here. Complete command and output below.
>>
>> /usr/local/bin/fio --name=global --ioengine=libaio --bsrange=16k-64k
>> --rw=randrw --iodepth=16 --direct=1 --verify=md5 --name=job0
>> --size=100m --filename=/fio/fio.dat --rw=randrw --rate=20m
>> --buffer_compress_percentage=80 --refill_buffers --buffer_pattern=123
>> --verify_dump=1
>
> You can't do a random read/write test, it'll fail on the reads that have
> not been populated. It might sometimes work if the file had been laid
> out prior with the right contents, but generally you cannot depend upon
> it. You want to do just --rw=randwrite and then the verify phase will
> take place after the writes are done, verifying those.
>
> Try and delete fio.dat prior to running this job, and it should fail
> consistently with or without buffer_compress_percentage.

I take it back, there is a bug there. Fio does skip verifying the reads 
we generate initially, and verifies the written data after the 
read/write phase. So it _should_ work, the fact that it doesn't is a 
bug. I'll take a look at it.

-- 
Jens Axboe