Re: Using swap though there's plenty of mem free

[Johnny Billquist <bqt%softjar.se@localhost>]

Unfortunately, Jonathan's observations aren't new or unique. This have been 
brought up before.
Apart from the fact that the unified memory is the reason this happens, and 
noone is willing to admit that it's far from perfect some times, the only thing 
that have come out is that perhaps the default values of various tuning knobs 
are far from ideal.

So it's back to tuning those knobs for Jonathan.
Personally, I run with:

vm.filemin=5
vm.filemax=10
vm.anonmin=5
vm.anonmax=80
vm.execmin=5
vm.execmax=50
vm.bufcache=5

Which atleast for me makes life better. But as usual, I guess I won't recommend 
anyone to adopt my settings, but just take them as a sugegstion on what they 
might want to tune on their own. Read the man-pages...

        Johnny

Greg A. Woods; Planix, Inc. skrev:
> On 1-May-08, at 12:10 PM, Jonathan Schleifer wrote:
> > Isn't there an option to tell NetBSD to stop that stupidity and free
> > the file cache when applications need it far more badly? I don't want
> > files cached that aren't used so often anyway. In this case, a 200 MB
> > file was cached that was only used once. That doesn't make any sense.
>
> Well if you can figure out how to get the machine to read your mind and 
> intuit your future needs, then maybe you'll have your wish granted!  :-)
>
> In the mean time the system is just doing the best it can given the 
> information it has and the configuration you've given it.
>
> You might consider dropping the file cache percentage significantly 
> (sysctl vm.filecache), but then you'd risk punishing every instance 
> where cached data could have been used just to foil the occasional case 
> where the system mistakenly caches a large file which only you in your 
> head know will never be accessed again.
>
> One hunch I have though is that the file cache is not as quickly cleaned 
> of pages from unlinked files (which also have no open descriptor 
> references) as it maybe could be.  Perhaps if the VM could be given a 
> hint about unlinked and un-referenced files then their pages could more 
> quickly be freed.  I may be mistaken though -- perhaps this already 
> happens and I've just been confused by some other issue.
>
> BTW, disabling swap won't necessarily have the best effect either -- you 
> may then be artificially creating pressure on the VM to keep rarely used 
> pages in active RAM which may then have unintended consequences.

--
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol