> Anyway, I think this points to something funny going on with the page
> loan code for pipes.  I don't know if this is exacerbated by running
> MP or what.  Obviously something is suboptimal with the default
> configuration choices here.

IPIs involved in page flipping can make it slow on MP systems.
we should use some kind of cpu-local mapping.

> Does anyone want to look into this further and try to figure out what's
> going on?  I don't have time to look at it anytime soon and it would
> be nice to track down the slowdown here or have more performant default
> settings.

IMHO, we should just kill sys_pipe.c and concentrate to improve socket code,
which also has page loan code these days.

YAMAMOTO Takashi