Comment # 16 on bug 911347 from Thomas Blume

(In reply to Bruno Pesavento from comment #15)
> Created attachment 619596 [details]
> Flushing times with SystemMaxFileSize=34M
> 
> Here are the results with SystemMaxFileSize=34M and no explicit limit to
> SystemMaxUse.
> Flush time grows to 25s, then cycles back to 57ms. No side effect visible to
> the user.
> Adding net.unix.max_dgram_qlen=1000 has no effect, apparently.

Hm, still 25s, not really good.
I'm currently looking at the upstream commits to improve journal flush
performance on btrfs (see comment#14).
Let's check wheter they can give some better results.
I will let you know when testbuilds are available.