On Tue, Jan 06, 2004 at 03:31:03PM +0100, Paul Kranenburg wrote:
> 
> The effect of the new buffer cache code on the vnode cache has already been
> noted. I would expect the drag you're experiencing to be largely eliminated
> if you'd revert the maximum memory use for the buffer to historic levels,
> i.e. to around 5% of physical memory.  To verify that this is the case,
> could you do
> 
> 	`sysctl -w vm.bufcache=5'
> 
> and see if that makes the symptoms go away?

I think the problem is actually that the backpressure on the actual amouont
of physmem through the call to buf_drain() in the pagedaemon isn't working,
because the memory is "released" through buf_mrelease(), which only calls
pool_put; this will not actually free pages back to the system, just to
the pool, which can grow without bound because the pools don't (and can't,
really) have separate highwater marks.

I would be interested to see what impact adding :

	pool_reclaim(&bmempools[buf_mempoolidx(size)]);

after the pool_put() call in buf_mrelease() would have.

Thor