Re: [PATCH] blk-wbt: get back the missed wakeup from __wbt_done

From: Jens Axboe
Date: Fri Aug 24 2018 - 14:50:51 EST

On 8/24/18 12:12 PM, Anchal Agarwal wrote:
> That's totally fair. As compared to before the patch it was way too high
> and my test case wasn't even running due to the thunderign herd issues and
> queue re-ordering. Anyways as I also mentioned before 10 times
> contention is not too bad since its not really affecting much the number of
> files read in my applciation. Also, you are right waking up N tasks seems
> plausible.

OK, I'm going to take that as a positive response. I'm going to propose
the last patch as the final addition in this round, since it does fix a
gap in the previous. And I do think that we need to wake as many tasks
as can make progress, otherwise we're deliberately running the device at
a lower load than we should.

> My application is somewhat similar to database workload. It does uses fsync
> internally also. So what it does is it creates files of random sizes with
> random contents. It stores the hash of those files in memory. During the
> test it reads those files back from storage and checks their hashes.

How many tasks are running for your test?

Jens Axboe