A Reddit user reported slow input-output operations on their btrfs system after upgrading the kernel to version 5.10.
I found a very simple way to reproduce the regression, namely extracting a large tarball, for example: tar xf firefox-84.0.source.tar.zst. On my external USB3 SSD with a Ryzen 5950x, it took almost 5 minutes in 5.10 compared to ~15s in kernel 5.9! To rule out filesystem fragmentation, I also tested a completely new, previously unused 1TB PCIe 4.0 SSD, showing a similar, though not as shocking regression from 5.2s to a colossal ~34 seconds or ~650% in 5.10 :-\/
It seems to be related to recent activity in the btrfs driver.
Message about the regression on the linux-btrfs mailing list.
Source: linux.org.ru
