Konstantin Khlebnikov [off-list ref] wrote:

quoted

Only do a wakeup in pipe_read() if we made space in a completely full
buffer.  The producer shouldn't be waiting on pipe->wait otherwise.

We could go further and wakeup writer only when at least half of buffer is
empty.  This gives better batching and reduces rate of context switches.

https://lore.kernel.org/lkml/157219118016.7078.16223055699799396042.stgit@buzz/T/#u (local)

Yeah, I saw that.  I suspect that where you put the slider may depend on the
context.

David