RE: [PATCH] x86: only use ERMS for user copies for larger sizes

[David Laight]

From: Linus Torvalds
> Sent: 22 November 2018 18:58
...
> Oh, and I just noticed that on x86 we expressly use our old "safe and
> sane" functions: see __inline_memcpy(), and its use in
> __memcpy_{from,to}io().
> 
> So the "falls back to memcpy" was always a red herring. We don't
> actually do that.
> 
> Which explains why things work.

It doesn't explain why I've seen single byte PCIe TLP generated
by memcpy_to/fromio().

I've had to change code to use readq/writeq loops because the
byte accesses are so slow - even when PIO performance should
be 'good enough'.

It might have been changed since last time I tested it.
But I don't remember seeing a commit go by.

	David

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