fedup speed

Zbigniew Jędrzejewski-Szmek zbyszek at in.waw.pl
Wed Dec 10 19:18:15 UTC 2014

I run fedup on a beefy desktop machine (SSD 450MB/s, 24GB ram, 12 cores),
and started wondering why is takes so much time (1.5h or thereabouts for
~4500 packages). I noticed two things:

1. installing packages used just 1 core, and actually not even not at 100%,
   and about 15MB/s were written to the disk.
   perf top said that time was spent mostly in lzma_decode.
   Is this expected?

2. at the end, fedup creates a log by running 'journalctl -a -m',
   which is --all --merge. This seems a bit excessive. On this machine
   I have 4.5 GB of logs from this machine, plus a few GB more from
   other sources. journalctl is not very fast (which is another issue),
   but even if it was, dumping all this is bound to be slow, and not
   particularly useful. 



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