> Il giorno 24 mag 2019, alle ore 08:51, Paolo Valente <paolo.valente@linaro.org> ha scritto:
> 
> 
> 
>> Il giorno 24 mag 2019, alle ore 01:43, Srivatsa S. Bhat <srivatsa@csail.mit.edu> ha scritto:
>> 
>> On 5/23/19 10:22 AM, Paolo Valente wrote:
>>> 
>>>> Il giorno 23 mag 2019, alle ore 11:19, Paolo Valente <paolo.valente@linaro.org> ha scritto:
>>>> 
>>>>> Il giorno 23 mag 2019, alle ore 04:30, Srivatsa S. Bhat <srivatsa@csail.mit.edu> ha scritto:
>>>>> 
>> [...]
>>>>> Also, I'm very happy to run additional tests or experiments to help
>>>>> track down this issue. So, please don't hesitate to let me know if
>>>>> you'd like me to try anything else or get you additional traces etc. :)
>>>>> 
>>>> 
>>>> Here's to you!  :) I've attached a new small improvement that may
>>>> reduce fluctuations (path to apply on top of the others, of course).
>>>> Unfortunately, I don't expect this change to boost the throughput
>>>> though.
>>>> 
>>>> In contrast, I've thought of a solution that might be rather
>>>> effective: making BFQ aware (heuristically) of trivial
>>>> synchronizations between processes in different groups. This will
>>>> require a little more work and time.
>>>> 
>>> 
>>> Hi Srivatsa,
>>> I'm back :)
>>> 
>>> First, there was a mistake in the last patch I sent you, namely in
>>> 0001-block-bfq-re-sample-req-service-times-when-possible.patch.
>>> Please don't apply that patch at all.
>>> 
>>> I've attached a new series of patches instead.  The first patch in this
>>> series is a fixed version of the faulty patch above (if I'm creating too
>>> much confusion, I'll send you again all patches to apply on top of
>>> mainline).
>>> 
>> 
>> No problem, I got it :)
>> 
>>> This series also implements the more effective idea I told you a few
>>> hours ago.  In my system, the loss is now around only 10%, even with
>>> low_latency on.
>>> 
>> 
>> When trying to run multiple dd tasks simultaneously, I get the kernel
>> panic shown below (mainline is fine, without these patches).
>> 
> 
> Could you please provide me somehow with a list *(bfq_serv_to_charge+0x21) ?
> 

Maybe I've found the cause. Please apply also the two patches attached and retry.

Thanks,
Paolo