> Il giorno 20 mag 2019, alle ore 12:19, Paolo Valente <paolo.valente@linaro.org> ha scritto:
> 
> 
> 
>> Il giorno 18 mag 2019, alle ore 22:50, Srivatsa S. Bhat <srivatsa@csail.mit.edu> ha scritto:
>> 
>> On 5/18/19 11:39 AM, Paolo Valente wrote:
>>> I've addressed these issues in my last batch of improvements for BFQ,
>>> which landed in the upcoming 5.2. If you give it a try, and still see
>>> the problem, then I'll be glad to reproduce it, and hopefully fix it
>>> for you.
>>> 
>> 
>> Hi Paolo,
>> 
>> Thank you for looking into this!
>> 
>> I just tried current mainline at commit 72cf0b07, but unfortunately
>> didn't see any improvement:
>> 
>> dd if=/dev/zero of=/root/test.img bs=512 count=10000 oflag=dsync
>> 
>> With mq-deadline, I get:
>> 
>> 5120000 bytes (5.1 MB, 4.9 MiB) copied, 3.90981 s, 1.3 MB/s
>> 
>> With bfq, I get:
>> 5120000 bytes (5.1 MB, 4.9 MiB) copied, 84.8216 s, 60.4 kB/s
>> 
> 
> Hi Srivatsa,
> thanks for reproducing this on mainline.  I seem to have reproduced a
> bonsai-tree version of this issue.

Hi again Srivatsa,
I've analyzed the trace, and I've found the cause of the loss of
throughput in on my side.  To find out whether it is the same cause as
on your side, I've prepared a script that executes your test and takes
a trace during the test.  If ok for you, could you please
- change the value for the DEVS parameter in the attached script, if
  needed
- execute the script
- send me the trace file that the script will leave in your working
dir

Looking forward to your trace,
Paolo