process load and swapping

process load and swapping

[Bob McElrath]

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I have been experiencing the following behavior on my alpha with many
kernel versions (2.4 series, latest is 2.4.19 with Ingo's O(1) scheduler
patch).

I'm running apache and zope, and when I load a zope page, the load jumps
to ~12 and the computer starts skipping.  That is, about once every 2s
the music (xmms) stops for ~0.5s and then comes back.  This repeats
every 2s until zope is finished creating the page (which takes sometimes
longer than a minute).  When the computer "skips", not only does the
music stop, but the mouse stops moving (i.e. I move it continuously and
it pauses for 0.5s every 2s).  This happens both at the console in X and
on virtual terminals (ssh'ed from another computer).  It's as if it's
not servicing interrupts for 0.5s.  Or does scheduling not occur when
the kernel decides to load N pages from swap, no matter how large N is?

This is totally due to swap use.  If I turn off all swap ('swapoff -a'),
the response of zope is speedy.  This behavior has happened with all
kernel versions I have used, at least since 2.4.17.

So, any ideas?  I know there have been arguments about the 'swappiness'
of this kernel, but the load going to 12 and interrupts not being
serviced is totally quantitative and totally repeatable...

Cheers,
-- Bob

Bob McElrath
Univ. of Wisconsin at Madison, Department of Physics

    "The surest way to corrupt a youth is to instruct him to hold in higher
    esteem those who think alike than those who think differently." 
        -- Nietzsche

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