https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=288856
Bug ID: 288856
Summary: freebsd-update slow
Product: Base System
Version: Unspecified
Hardware: Any
OS: Any
Status: New
Severity: Affects Many People
Priority: ---
Component: misc
Assignee: [email protected]
Reporter: [email protected]
For any computer with small memory (such as sub-1G), such as embedded system,
small raspberry, etc, freebsd-update is extremely slow when going upgrade. It
seems that many people as seeing this.
This is typically not I/O bound (fast ssd's mirrored with gmirror, systat shows
%busy few percent) nor it is network bound (doing install, so no more network
activity, and our network connectivity is 10G with beefy internal network).
Symptom seems to be high system load %.
I am usually doing this on gmirrored ssd's, but others seem to see this on zfs
root as well.
Theory: One possible reason seems to be that /var/db/freebsd-update/files has
very large number of files in a single directory, for example, right now in the
system I am doing "freebsd-update install", it has 124211 files at this moment.
systat first showed 99.5% system time, and after a while system time becomes
around 70%. According to systat, dir-cache only gets 1% hit ratio, if that is
relevant?
In systems with considerably larger memory this effect is not clearly visible,
though that might also be faster cpus. There seems to be similar reports when
running freebsd-update in a VM with small memory allocation so it might be that
fast cpu does not help.
Suggestion: as the file names are hashed anyway, take, say two first letters,
and build a/b/abf222etcfullhashedname.gz directory hierachy, keeping the
directories smaller.
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