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SubjectRe: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation
On 10-11-18 04:50 PM, James Bottomley wrote:
> Before we go gung ho on this, there's no evidence that N discontiguous
> ranges in one command are any better than the ranges sent N times ...
> the same amount of erase overhead gets sent on SSDs.

No, we do have evidence: execution time of the TRIM commands on the SSD.

The one-range-at-a-time is incredibly slow compared to multiple ranges at a time.
That slowness comes from somewhere, with about 99.9% certainty that it is due
to the drive performing slow flash erase cycles.

I think perhaps we should do the batching as much as possible,
and then split them into single ranges for LLDs that cannot handle multi-ranges.

Way more efficient that way.


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