On Sat, Jan 07, 2012 at 03:56:48PM +1100, Chris Samuel wrote:
This looks like the thread:
http://comments.gmane.org/gmane.comp.file-systems.btrfs/15027
ta. interesting thread.
Because XFS doesn't remember what was trimmed so sends the same list (plus any new ones) down to the FS I'd guess.
that's weird. if they're already trimmed, why is it sending the same blocks? makes me wonder how it's building the list of blocks-to-be-trimmed. hmmm...probably the full list of free blocks, whereas ext4 sends the full list minus those it knows it has already trimmed (an obvious when you think about it, but still clever optimisation).
what is it actually counting here? bytes in data blocks that (might) need trimming? byte-counts in TRIM commands sent to the device? something else?
Not a clue I'm afraid - this man page indicates its bytes the FS has sent to the block layer to be trimmed:
http://manpages.ubuntu.com/manpages/oneiric/man8/fstrim.8.html
yep, I read the man page, wasn't really expecting an answer from you...just wondering aloud :) craig -- craig sanders <cas@taz.net.au> BOFH excuse #11: magnetic interference from money/credit cards