On Mon, Dec 3, 2018 at 1:04 PM Lionel Bouton <lionel-subscript...@bouton.name> wrote: > > Le 03/12/2018 à 20:56, Lionel Bouton a écrit : > > [...] > > Note : recently I tried upgrading from 4.9 to 4.14 kernels, various > > tuning of the io queue (switching between classic io-schedulers and > > blk-mq ones in the virtual machines) and BTRFS mount options > > (space_cache=v2,ssd_spread) but there wasn't any measurable improvement > > in mount time (I managed to reduce the mount of IO requests > > Sent to quickly : I meant to write "managed to reduce by half the number > of IO write requests for the same amount of data writen" > > > by half on > > one server in production though although more tests are needed to > > isolate the cause).
Interesting. I wonder if it's ssd_spread or space_cache=v2 that reduces the writes by half, or by how much for each? That's a major reduction in writes, and suggests it might be possible for further optimization, to help mitigate the wandering trees impact. -- Chris Murphy
