Re: commit 01e99aeca397 causes longer runtime of block/004

Ming Lei
2020-03-04T03:47:01Z

On Wed, Mar 04, 2020 at 02:38:43AM +0000, Shinichiro Kawasaki wrote:
> I noticed that blktests block/004 takes longer runtime with 5.6-rc4 than
> 5.6-rc3, and found that the commit 01e99aeca397 ("blk-mq: insert passthrough
> request into hctx->dispatch directly") triggers it.
>
> The longer runtime was observed with dm-linear device which maps SATA SMR HDD
> connected via AHCI. It was not observed with dm-linear on SAS/SATA SMR HDDs
> connected via SAS-HBA. Not observed with dm-linear on non-SMR HDDs either.
>
> Before the commit, block/004 took around 130 seconds. After the commit, it takes
> around 300 seconds. I need to dig in further details to understand why the
> commit makes the test case longer.
>
> The test case block/004 does "flush intensive workload". Is this longer runtime
> expected?

The following patch might address this issue:

https://lore.kernel.org/linux-block/20200207190416.99928-1-sqazi@google.com/#t

Please test and provide us the result.

thanks,
Ming