Hi Josef,
> On 24. Dec 2020, at 19:09, Josef Bacik <[email protected]> wrote:
>
> On 12/21/20 2:45 PM, René Rebe wrote:
>> Hey there,
>> as a long time btrfs user I noticed some some things became very slow
>> w/ Linux kernel 5.10. I found a very simple test case, namely extracting
>> a huge tarball like:
>> tar xf /usr/src/t2-clean/download/mirror/f/firefox-84.0.source.tar.zst
>> Why my external, USB3 road-warrior SSD on a Ryzen 5950x this
>> went from ~15 seconds w/ 5.9 to nearly 5 minutes in 5.10, or 2000%
>> To rule out USB, I also tested a brand new PCIe 4.0 SSD, with
>> a similar, albeit not as shocking regression from 5.2 seconds
>> to ~34 seconds or∫~650%.
>> Somehow testing that in a VM did over virtio did not produce
>> as different results, although it was already 35 seconds slow
>> with 5.9.
>> # first bad commit: [38d715f494f2f1dddbf3d0c6e50aefff49519232]
>> btrfs: use btrfs_start_delalloc_roots in shrink_delalloc
>> Now just this single commit does obviously not revert cleanly,
>> and I did not have the time today to look into the rather more
>> complex code today.
>> I hope this helps improve this for the next release, maybe you
>> want to test on bare metal, too.
>
> Alright to close the loop with this, this slipped through the cracks because
> I was doing a lot of performance related work, and specifically had been
> testing with these patches on top of everything
>
> https://lore.kernel.org/linux-btrfs/[email protected]/
>
> These patches bring the performance up to around 40% higher than baseline
I indeed tested the linux-btrfs for-5.11 and found the performance some 50%
better. I would hope that can be brought back to 5.9 levels sometime soon ;-)
> . In the meantime we'll probably push this partial revert into 5.10 stable
> so performance isn't sucking in the meantime. Thanks,
That certainly makes sense for the LTS kernel series.
Thanks for looking into this,
Merry Christmas,
René Rebe
--
ExactCODE GmbH, Lietzenburger Str. 42, DE-10789 Berlin, https://exactcode.com
https://exactscan.com | https://ocrkit.com | https://t2sde.org |
https://rene.rebe.de
