copy on write for splice() from file to pipe?

Linus Torvalds torvalds at
Thu Feb 9 19:36:02 UTC 2023

On Thu, Feb 9, 2023 at 11:17 AM Stefan Metzmacher <metze at> wrote:
> Any comment about the idea of having a preadv2() flag that
> asks for a dma copy with something like async_memcpy() instead
> of the default that ends up in copy_user_enhanced_fast_string()?

I guarantee that you will only slow things down with some odd async_memcpy.

There are zero DMA engines that do memory copying better than memcpy -
the only way you can do better if is the destination isn't memory in
the first place but the final device, and then we just call it "dma".


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