RE: [PATCH V2 0/2] mmc: block: Support Host to control FUA

[Christian Löhle]

> 
> Unless there is something special / wrong with sdhci-sprd (unlikely? Its just a flag) or your eMMC (maybe more likely?) then Id expect this or similar performance degradation for any host controller and eMMC.
> I can redo some measurement if you provide your workload.
> But I'd say if you don’t want to pay the price of reliable write then make sure to not issue them, by not issuing FUA?
> Maybe I'm misunderstanding, but why would the host controller driver control FUA?
> 

Maybe one more point on that: Compare performance with fua disabled but cache off, should be comparable unless there is an actual reliable write problem.
If reliable write is performing horribly on that eMMC maybe a quirk could be thought of.
Anyway your 13MB/s random with fua, if a reliable write is basically always active for a given cache size,
doesn't sound totally unreasonable (over 3000 IOPS, assuming 4k writes).

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