On Tue, Apr 03, 2001 at 02:11:07PM +0200, Frank van der Linden wrote:
> The UBC + interactive performance thing came up again in some internal
> discussion recently, but this is a better place for it.
> 
> First of all, there still seem to be some complains about bad
> interactive performance (i.e. program ("text") pages being
> paged out because they're being claimed for data).
> 
> I noticed that the default value for 'vtextmin', the minimum threshold
> for the percentage of pages dedicated to text, is currently 5%. Which
> is a bit low, even at 512M this would only get you 25M, which is
> easily exceeded by just running X and netscape or mozilla. People
> who are seeing problems might want to try setting this at a higher
> value of, say, 20%.

I'll question your math here...
looking at the netscape on my machine, the total text size for netscape
and all the shared libraries it uses is about 14 MB, and most data-section
pages are probably modified and thus would could as "anon" pages in UVM
and not "vtext".  this should easily fit in 25 MB (if shared libs were
accounted properly, which they're not).


> Maybe another simple thing to try is 'don't touch text pages, unless
> the data pages fall below a certain threshold'. This would
> be easy to do (it's all in lines 451-478 in uvm_pdaemon.c).

that might be interesting, we should do some experiments.


> Lastly, I believe that another problem was that shared libraries
> are treated the same as 'normal' data files. Not sure what to
> do there, maybe a heuristic that prefers keeps r-x mapped pages?

yea, this was mentioned before but I haven't had time to experiment.

for both of these ideas, it'd be nice if someone could post diffs
so that the people who are reporting problems can try them.

-Chuck