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    SubjectRe: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation
    Jeff Moyer wrote:
    > James Bottomley <> writes:
    > > Not stepping into the debate: I'm happy to see punch go to the mapping
    > > data and FITRIM pick it up later.
    > >
    > > However, I think it's time to question whether we actually still want to
    > > allow online discard at all. Most of the benchmarks show it to be a net
    > Define online discard, please.
    > > lose to almost everything (either SSD or Thinly Provisioned arrays), so
    > > it's become an "enable this to degrade performance" option with no
    > > upside.
    > Some SSDs very much require TRIMming to perform well as they age. If
    > you're suggesting that we move from doing discards in journal commits to
    > a batched discard, like the one Lukas implemented, then I think that's
    > fine. If we need to reintroduce the finer-grained discards due to some
    > hardware changes in the future, we can always do that.

    "Growable" virtual disks benefit from it too, if it frees up a lot of space.

    Windows has some ability to trim unused space in NTFS on virtual disks
    for this reason; I'm not sure if it's an online or offline procedure.

    Online trim may be slow, but offline would be awfully inconvenient
    when an fs is big and needed for a live system, or when it's your root fs.

    -- Jamie

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