On Wed, Dec 23, 2020 at 7:12 PM Theodore Y. Ts'o <tytso@xxxxxxx> wrote: > > On Wed, Dec 23, 2020 at 01:47:33AM +0100, Matteo Croce wrote: > > As an extra test I extracted the archive with data=ordered, remounted > > with data=writeback and timed the rm -rf and viceversa. > > The mount option is the one that counts, the one using during > > extraction doesn't matter. > > Hmm... that's really surprising. At this point, the only thing I can > suggest is to try using blktrace to see what's going on at the block > layer when the I/O's and discard requests are being submitted. If > there are no dirty blocks in the page cache, I don't see how > data=ordered vs data=writeback would make a difference to how mount -o > discard processing would take place. > Hi, these are the blktrace outputs for both journaling modes: # dmesg |grep EXT4-fs |tail -1 [ 1594.829833] EXT4-fs (nvme0n1p1): mounted filesystem with ordered data mode. Opts: data=ordered,discard # blktrace /dev/nvme0n1 & sleep 1 ; time rm -rf /media/linux-5.10/ ; kill $! [1] 3032 real 0m1.328s user 0m0.063s sys 0m1.231s # === nvme0n1 === CPU 0: 0 events, 0 KiB data CPU 1: 0 events, 0 KiB data CPU 2: 0 events, 0 KiB data CPU 3: 1461 events, 69 KiB data CPU 4: 1 events, 1 KiB data CPU 5: 0 events, 0 KiB data CPU 6: 0 events, 0 KiB data CPU 7: 0 events, 0 KiB data Total: 1462 events (dropped 0), 69 KiB data # dmesg |grep EXT4-fs |tail -1 [ 1734.837651] EXT4-fs (nvme0n1p1): mounted filesystem with writeback data mode. Opts: data=writeback,discard # blktrace /dev/nvme0n1 & sleep 1 ; time rm -rf /media/linux-5.10/ ; kill $! [1] 3069 real 1m30.273s user 0m0.139s sys 0m3.084s # === nvme0n1 === CPU 0: 133830 events, 6274 KiB data CPU 1: 21878 events, 1026 KiB data CPU 2: 46365 events, 2174 KiB data CPU 3: 98116 events, 4600 KiB data CPU 4: 290902 events, 13637 KiB data CPU 5: 10926 events, 513 KiB data CPU 6: 76861 events, 3603 KiB data CPU 7: 17855 events, 837 KiB data Total: 696733 events (dropped 0), 32660 KiB data Cheers, -- per aspera ad upstream
