rsync at booting can take too much time

[yvs2014]

Lately I've noticed that booting is too slow on a couple systems (ubuntu25.10 and debian13 if it matters) with enabled log2ram service, to find out what's on and disabling "quiet splash" on one (ubuntu) of them - spotted out a line like Job log2ram.service/start running (Ns/1min 57s). It's timed out in ~2min. In logs I can see messages like:

22:40:54 <previous message in log>
22:42:57 log2ram[1270]: building file list ... done
22:42:57 log2ram[1556]: <first line with some file>
22:42:57 log2ram[1556]: <last line with some file>

After disabling (suppose so) rsync with USE_RSYNC=false it got about 30sec at that Job log2ram.service/start running point .

Is there a way to speed up a bit rsync on that 'building file list'? (if I got it correctly, it's the slowest operation at boot)

p.s. in log2ram.conf there are SIZE=4G and PATH_DISK="/var/log;/home/myusername/.cache", and du -sh /var/log /home/myusername/.cache displays ~250M and ~1G respectively

[yvs2014]

Btw, what about setting sync/copy behaviour in different way
at start/boot: copying from-disk-to-ram
at runtime/shutdown: syncing from-ram-to-disk

I've tried two variants to speed up boot time a bit with

1. behaviour is closer to cp with rsync options --whole-file --no-checksum in disk2ram case
   like c089c79
2. cp for disk2ram and rsync for ram2disk (by setting RSYNC_FROM_DISK=false in config file)
   like 357e6e6

Looks like it sufficiently reduces boot time in my environment described in previous comment.
Is there any pitfalls with this approach, or I'm missing something?

[azlux]

Hi,
rsync should not take such long time to sync folder.
After booting, Can you try to copy log files :
time rsync -aAXv --sparse --inplace --no-whole-file --delete-after "/var/log/" "/tmp/somewhere/"
then try with
time cp -rfup --sparse=always /var/log/" "/tmp/somewhere" -T "$RAM_LOG"/

Is after booting the same difference ? Since I use standard tool, you should not have 2min+ of copy.

[yvs2014]

rsync should not take such long time to sync folder. After booting, Can you try to copy log files : time rsync -aAXv --sparse --inplace --no-whole-file --delete-after "/var/log/" "/tmp/somewhere/" then try with time cp -rfup --sparse=always /var/log/" "/tmp/somewhere" -T "$RAM_LOG"/

To compare copy time of those dirs when system is already booted and works with all its boosts (i.e. more likely it's already cached, in buffers, etc.)

# systemctl stop log2ram

# df -h | grep /tmp
tmpfs           8,0G  644K  8,0G   1% /tmp

# mkdir /tmp/by-rsync /tmp/by-copy

# cat ./by-rsync.sh
#!/usr/bin/env bash
for d in $@; do
  rsync -aXv --sparse --inplace --no-whole-file --delete-after "$d"/ /tmp/by-rsync/ |& tee -a /var/log/tst.log
done

# cat ./by-copy.sh
#!/usr/bin/env bash
for d in /var/log ~/.cache; do
  cp -rfup --sparse=always "$d"/ -T /tmp/by-copy/ 2>&1 | tee -a /var/log/tst.log
done

# time ./by-rsync.sh /var/log /home/yvs/.cache
./by-rsync.sh /var/log /home/yvs/.cache  1,64s user 5,59s system 145% cpu 4,975 total

# time ./by-copy.sh /var/log /home/yvs/.cache
./by-copy.sh /var/log /home/yvs/.cache  0,03s user 1,18s system 99% cpu 1,209 total

got that copy more than 4times faster than rsync at copying the whole dirs with a lot of files in this case

Is after booting the same difference? Since I use standard tool, you should not have 2min+ of copy.

Maybe (not sure) it's connected with some buffering and other things at system booting, but yes it's slower at boot-time with both copy and sync.

Anyway, what about using cp or copy-like rsync options at boot-time (when there's no need in a full-featured synchronization)? And rsync at runtime/shutdown when there are clear advantages of synchronization.