On 2019-02-10 16:35, Niclas Zeising wrote:
On 2019-02-08 10:27, Alexander Leidinger wrote:
I recently noticed some generic slowness myself. I experienced this
during replacing disks in a raidz by bigger ones. Long story short,
check top -s if you have vnlru running for a long period at high
CPU... If yes increase kern.maxvnodes (I increased to 10 times). Note,
we should improve the admin page in the FAQ, the vnlru entry could
need a little bit more hints and explanations.
If you encounter the same issue we have probably introduced a change
somewhere with an unintended side effect.
I'm seeing this as well, on 13-CURRENT. I updated a computer from the
last January snapshot (30 or 31 of January, I can't remember) and it
seems disk IO is very slow. I remember having a svn checkout taking a
very long time, with the SVN process pegged at 100% according to top. I
can't see the vnlru process running though, but I haven't looked
closely, and I haven't tried the maxvnodes workaround. Something has
This is systems using ZFS, both mirror and single disk. Gstat shows
disks are mostly idle.
I know this is a lousy bug report, but this, and the feeling that things
are slower than usual, is what I have for now.
I did some more digging. In short, disabling options COVERAGE and
options KCOV made my test case much faster.
create a new zfs dataset (zroot/home/test in my case)
time a checkout of https://svn.freebsd.org/base/head, putting the files
in the new zfs dataset.
This is in no way scientific, since I only ran the test once on each
kernel, and using something on the network means I'm susceptible to
varying network speeds and so on, but.
In this specific scenario, using a kernel without those options, it's
about 3 times faster than with, at least on the computer where I ran the
I noticed in the commit log that the coverage and kcov options has been
disabled again, albeit for a different reason. Perhaps they should
remain off, unless the extra runtime overhead can be disabled in
runtime, similar to witness.
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