[dm-devel] [PATCH] x86: optimize memcpy_flushcache

[Dan Williams]

On Wed, Jun 27, 2018 at 4:23 AM, Yigal Korman <yigal at plexistor.com> wrote:
> Hi,
> I'm a bit late on this but I have a question about the original patch -
> I thought that in order for movnt (movntil, movntiq) to push the data
> into the persistency domain (ADR),
> one must work with length that is multiple of cacheline size,
> otherwise the write-combine buffers remain partially
> filled and you need to commit them with a fence (sfence) - which ruins
> the whole performance gain you got here.
> Am I wrong, are the write-combine buffers are part of the ADR domain
> or something?

The intent is to allow a batch of memcpy_flushcache() calls followed
by a single sfence. Specifying a multiple of a cacheline size does not
necessarily help as sfence is still needed to make sure that the movnt
result has reached the ADR-safe domain.