[ale] VM: do_try_to_free_pages failed for kswapd

[Joseph A Knapka]

John Wells wrote:
> 
> My post earlier about IMAP/Apache/Squirrel mail running extremely long
> turned out to have nothing to do with the machine's speed.  When I returned
> home tonight, I checked the machine and found numerous "VM:
> do_try_to_free_pages failed for kswapd".  I hit a key a few times and got to
> a prompt, but everything was moving *extremely* slow.
> 
> I looked at how many httpd processes were running and there were 29!  A bit
> more than I expected.  I "apachectl stop"ped and the screen was filled with
> "VM: do_try_to_free_pages failed for httpd", and I couldn't regain control
> of the machine...had to do a hard reboot.
> 
> What might be causing this?

It means that the kernel is unable to find any free
pages, and was furthermore unable even to find any
pages to swap out. This means that a great many
pages on your system are being used in non-
swappable contexts, such as device driver allocs
or network buffers. If this is a low-memory
machine that's being used as a server or router,
I'd bet on the latter. Make sure you don't have
"allow large windows" enabled in the kernel network
configuration.

Of course, it could also happen because of a
kernel bug :-)

>  I'm running kernel 2.2.17 and everything I've
> found on the net regarding similar messages indicate a problem with kernel
> 2.2.16 that was supposedly fixed in 2.2.17.  I'm betting that the kernel is
> unable to free the memory used by various processes and that's why my system
> was dragging so badly.

Process memory is always swappable; it's internal
kernel allocations that cause this kind of trouble.

>  I plan on recompiling a newer kernel, but could
> someone provide some insight into what exactly might be happening?

Motto: "Our answers are better than a poke in the
eye with a sharp stick!"

Cheers,

-- Joe
    Any OS distinguishable from Windows is not sufficiently broken.

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