Re: 2.2.19pre6aa1 degraded performance for me...

[Andrea Arcangeli]

On Mon, Jan 08, 2001 at 10:46:29PM +0100, Sasi Peter wrote:
> What I had w/2.2.18pre19 (+raid+ide):
> ~80MB more in cache and ~80MB swapped out (eg. currently unused notes
> server and squid) There is enough of swap over 3 disks (like the
> raid), so I did not bother disabling squid and notes, since - I thought -
> they would only take up some swap unused.

There are many variables. However I guess the slowdown is because your idle
apps didn't got swapped out in favour of cache as you noticed. An aggressive
aging algorithm would probably fix that but it then would hurt other cases
(after you don't need a frequenty accessed part of filesystem cache anymore it
would take ages before it gets collected potentially causing an unnecessary
swapout storms because the kernel doesn't know you don't need such cache
anymore).  Furthmore if notes and squid are rarely running but they provides
critical services if they would go totally into swap in favour of fs cache you
would get very bad latencies the first time somebody connects to the server. So
the fix I suggest you is to buy more ram or to shutdown squid and notes. Than
you may as well see a performance improvement compared to 2.2.18pre19
(+raid+ide).  Otherwise you can push the machine low on memory a bit until they
both goes totally into swap (check with `ps v`). Hope this helps.

Andrea