[igt-dev] [PATCH igt] lib: Provide an accelerated routine for readback from WC

[Eric Anholt]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Reading from WC is awfully slow as each access is uncached and so
> performed synchronously, stalling for the memory load. x86 did introduce
> some new instructions in SSE 4.1 to provide a small internal buffer to
> accelerate reading back a cacheline at a time from uncached memory, for
> this purpose.

I think without a _mm_mfence() before the movntdqas, you can get stale
results from movntdqa's little cache.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 832 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/igt-dev/attachments/20180227/26b1e74f/attachment.sig>