Hello,
It's something I've been observing for a while, but substitutes are very
IO intensive (as can be seen in iotop, the substitute process is waiting
on IO > 99% of the time) and is much slower than expected (3 minutes to
transfer 100 MiB uncompressed over a 50 mbps downstream link):
--8<---------------cut here---------------start------------->8---
TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND
13934 be/4 root 1033.09 K/s 1485.06 K/s 0.00 % 93.36 % guile \
/gnu/store/vphx2839xv0qj9xwcwrb95592lzrrnx7-guix-1.3.0-3.50dfbbf/bin/guix
substitute --substitute
--8<---------------cut here---------------end--------------->8---
The publisher (remote machine) is has its guix-daemon configured via:
--8<---------------cut here---------------start------------->8---
(service guix-publish-service-type
(guix-publish-configuration
(advertise? #t)
(compression '(("zstd" 3)))
(host "0.0.0.0"))) ;listen on all interfaces
--8<---------------cut here---------------end--------------->8---
CPU is idling during on both sides during the transfer (all the work
appears to be in the IO on the receiving end).
The above example was observed downloading
/gnu/store/4fcwwlv9bzfrraxiz41b4vcv131930fx-libstdc++-doc-9.4.0, but I
do not think it is substitute-specific.
Maxim
