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    SubjectRe: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation
    On 10-11-18 12:19 PM, James Bottomley wrote:
    >
    > 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
    > lose to almost everything (either SSD or Thinly Provisioned arrays), so
    > it's become an "enable this to degrade performance" option with no
    > upside.

    I also suspect that online TRIM exerts significant premature wear on the SSDs.
    TRIM operations most likely trigger immediate copy/erase operations internal
    to most SSDs, often regardless of the amount of data being trimmed.

    Performing a 256KB erase because of a 1024-byte TRIM, over and over, is going
    to harm the expected lifetime of an SSD. Sure, some SSDs may do things differently
    internally, but I don't see it working that way in much of the current crop of SSDs.

    Currently, I patch my kernels to remove the automatic online TRIMs.
    Is there a knob somewhere for this in the later kernels?

    Cheers


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