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.
Greetings,
René https://youtu.be/NhUMdvLyKJc
--
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