Subject: Re: Strange VM behaviour
To: Chuck McManis <>
From: Lennart Augustsson <>
List: tech-kern
Date: 02/04/2001 15:57:27
Chuck McManis wrote:

> At 03:20 PM 2/4/01 -0500, Lennart Augustsson wrote:
> >Note that when my machine
> >freezes there is NO disk activity.
> Wild theory time: The page scanner is scanning a zillion pages.

Well, perhaps.  If scanning a page is really slow.  I've got a
300 MHz Pentium with 128MB memory.  Scanning 128MB worth
of pages would give about 30 us/page for a 5 second pause.

> When this happens have you tried popping into ddb and snooping around to
> see what process is active and what the queues look like?

I've not managed to get in to DDB.  I'm always running X when this happens
so I'd need to swap consoles.

> I'm guessing
> you've got a fair bit of memory and you're stuck in the page scanner (which
> appears to lock everything out to prevent the pages being modified while it
> is scanning them.) Try taking your system down to 16MB and see if that
> doesn't actually get you a bit better performance.

Arrghh!  With 16MB my machine would stand still.  When this happens I
usually have a 100 MB compilation and Netcrap which wants another 50M.
Plus the usual assortment of sundry processes.  So I can't even imagine running
this with 16M memory.

    -- Lennart