Re: emap

[Mindaugas Rasiukevicius <rmind%netbsd.org@localhost>]

yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi) wrote:
> hi,
> 
> what's the status of emap and pipe?
> 

If I remember correctly, I could not get real performance improvement
of pipe with UVM emap.  Higher chances are that it would improve socket
performance.  Also, pipe has direct I/O disabled (PIPE_NODIRECT) due
to some rare lock-ups when switching between direct/buffered.  AFAIK,
we have this bug since netbsd-3 times or even earlier.

However, I tend to question whether UVM emap was a right approach to
the problem.  For amd64, we should definitely have a direct mapping
of kernel space (I was planning to revive the patch written by chs@,
but ran out of time) and encourage our users to use amd64 instead
of i386.  Most other architectures have a segment for direct mapping.
I wonder if we could help i386 with large pages for kernel space..

-- 
Mindaugas