My reply din't seem to get through the mailing list. Blame HTML
enabled on my mobile. :)
Again. Sorry for top posting. Thought i was continuing the thread :(
Thanks for clarification on refill_buffers. I get FIO now after trials
and help from you guys.
--
Srinivasa Chamarhy
--
Srinivasa R Chamarthy
On Thu, May 7, 2015 at 11:30 PM, Srinivasa Chamarthy
<chamarthy.raju@xxxxxxxxx> wrote:
> Sorry for that. Thanks for clarification on refill_buffers.
>
> On 07-May-2015 10:27 pm, "Jens Axboe" <axboe@xxxxxxxxx> wrote:
>>
>> On 05/06/2015 09:58 PM, Srinivasa Chamarthy wrote:
>>>
>>> Thanks Eaton. One question thought. From the man page for refill_buffers:
>>>
>>> "If this option is given, fio will refill the IO buffers on every
>>> submit. The default is to only fill it at init time and reuse that
>>> data. Only makes sense if zero_buffers isn't specified, naturally. If
>>> data verification is enabled, refill_buffers is also automatically
>>> enabled."
>>>
>>> Every IO submitted will have a new pattern for repeated workloads?
>>> using refill_buffers, i seem to get same pattern repeatedly. Is that
>>> how it should be? i was under the impression that refill will use new
>>> pattern every time.
>>>
>>> # fio --filename=test_refill --readwrite=randwrite --size=1m
>>> --refill_buffers --bs=256k --norandommap --name=refill
>>> # for each in {0..3}; do dd if=test_refill bs=262144 count=1
>>> skip=$each 2>/dev/null | md5sum; done
>>> 86c3e47e173a58ad93470fd8db856f8c -
>>> 6fe5ce86d04522889c99809d6d97cb94 -
>>> 9113ce00f3781861afc41aaf6da32428 -
>>> f0b575c40e9da23b524f585723cbea4e -
>>>
>>> # fio --filename=test_refill --readwrite=randwrite --size=1m
>>> --refill_buffers --bs=256k --norandommap --name=refill
>>> # for each in {0..3}; do dd if=test_refill bs=262144 count=1
>>> skip=$each 2>/dev/null | md5sum; done
>>> 86c3e47e173a58ad93470fd8db856f8c -
>>> 6fe5ce86d04522889c99809d6d97cb94 -
>>> 9113ce00f3781861afc41aaf6da32428 -
>>> f0b575c40e9da23b524f585723cbea4e -
>>
>>
>> First of all, please stop top posting. It breaks the flow of
>> conversations.
>>
>> Secondly, this is expected behavior, and it's done to get identical
>> behavior between runs. If you had longer runs, each buffer would be
>> different. But if you did a new run after that, the sequence of buffers
>> would be the same. Same thing happens with the offsets generated, the buffer
>> lengths generated, etc.
>>
>> If you want a truly different run everytime, you have a few options. One
>> is to simply set randrepeat=0, then OS entropy will seed the random
>> generators. Or you can use randseed= to set a specific seed, which would
>> allow you to reproduce a specific run.
>>
>>
>> --
>> Jens Axboe
>>
>
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