Re: CVS commit: src/sys/miscfs/genfs

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

> yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi) wrote:
> > > > because pager map is a system-global resource.
> > > 
> > > Address space is managed by UVM, with appropriate locking. At the unmap
> > > point, there are no references to KVA. Can you explain more?
> > 
> > keeping the map longer can block other threads.
> 
> See your point now. I think the window is very small (cf. the case when
> mapout is left for aiodone) and this has a positive effect for glock.
> 
> Do you think such window has any relevant effect to the pager map?

you changed the code from:

        pagermapout
        GOP_ALLOC
        unlock glock

to:

        GOP_ALLOC
        unlock glock
        pagermapout

note that GOP_ALLOC is likely far more expensive than pagermapout.
while your change makes the glock be released a little earlier,
it makes pager map kept while doing potentially very expensive GOP_ALLOC.

so my guess is different from yours; a nagative effect is bigger.

YAMAMOTO Takashi

> 
> > 
> > YAMAMOTO Takashi
> 
> -- 
> Best regards,
> Mindaugas