YAMAMOTO Takashi wrote:

> > 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.

I just tried a UP NetBSD 3.1 system.  With kern.pipe.maxloankvasz at
default (16MB) I get:

-b 1k    74.04 MB/s
-b 4k   112.38 MB/s
-b 7k   166.79 MB/s
-b 8k   166.87 MB/s
-b 32k  230.22 MB/s
-b 64k  226.93 MB/s

and with kern.pipe.maxloankvasz set to 0 I get:

-b 1k    78.22 MB/s
-b 4k   205.99 MB/s
-b 7k   239.62 MB/s
-b 8k   351.07 MB/s
-b 32k  630.09 MB/s
-b 64k  790.75 MB/s

So doesn't appear to be an IPI or general MP issue.

Simon.