> > because tmpfs doesn't know the fact that some memory like buffer cache
> > can be reclaimed on-demand, it behaves too conservatively if memory is
> > filled up with caches.
> 
> Can I work around this with the right choice of vm settings?  Setting very
> high vm.anon{min,max} and vm.file{min,max} = {0,1} didn't help.
> 
> Is uvm_wait() the right thing to do in tmpfs_reg_resize() when there
> are insufficient free pages?

no and no.

IMO removing tmpfs auto-sizing feature is a way to go.
ie. mandate -s option of mount_tmpfs and trust it.

teaching tmpfs about vm details can be an alternative.
but i don't think it's realistic or desirable.

YAMAMOTO Takashi