Re: [PATCH BUGFIX/IMPROVEMENT 0/3] three bfq fixes restoring service guarantees with random sync writes in bg

[Paolo Valente]

> Il giorno 31 ago 2017, alle ore 08:41, oleksandr@xxxxxxxxxxxxxx ha scritto:
> 
>> Tested-by: Oleksander Natalenko <oleksandr@xxxxxxxxxxxxxx>
> 
> I'm "Oleksandr" :).
> 

Sorry, resending ...

Paolo

> 31.08.2017 08:10, Paolo Valente wrote:
>> Hi,
>> while testing the read-write unfairness issues reported by Mel, I
>> found BFQ failing to guarantee good responsiveness against heavy
>> random sync writes in the background, i.e., multiple writers doing
>> random writes and systematic fdatasync [1]. The failure was caused by
>> three related bugs, because of which BFQ failed to guarantee to
>> high-weight processes the expected fraction of the throughput.
>> The three patches in this series fix these bugs. These fixes restore
>> the usual BFQ service guarantees (and thus optimal responsiveness
>> too), against the above background workload and, probably, against
>> other similar workloads.
>> Thanks,
>> Paolo
>> [1] https://lkml.org/lkml/2017/8/9/957
>> Paolo Valente (3):
>>  block, bfq: make lookup_next_entity push up vtime on expirations
>>  block, bfq: remove direct switch to an entity in higher class
>>  block, bfq: guarantee update_next_in_service always returns an
>>    eligible entity
>> block/bfq-iosched.c |  4 +--
>> block/bfq-iosched.h |  4 +--
>> block/bfq-wf2q.c    | 91 ++++++++++++++++++++++++++++++++---------------------
>> 3 files changed, 60 insertions(+), 39 deletions(-)
>> --
>> 2.10.0