On Tuesday 03 November 2009, you wrote:
> > With a representative test I get 0 for kswapd_slept_prematurely.
> > Tested with .32-rc6 + patches 1-3 + this patch.
>
> Assuming the problem actually reproduced, can you still retest with the

Yes, it does.

> patch I posted as a follow-up and see if fast or slow premature sleeps
> are happening and if the problem still occurs please? It's still
> possible with the patch as-is could be timing related. After I posted
> this patch, I continued testing and found I could get counts fairly
> reliably if kswapd was calling printk() before making the premature
> check so the window appears to be very small.

Tested with .32-rc6 and .31.1. With that follow-up patch I still get 
freezes and SKB allocation errors. And I don't get anywhere near the fast, 
smooth and reliable behavior I get when I do the congestion_wait() 
reverts.

The new case does trigger as you can see below, but I'm afraid I don't see 
it making any significant difference for my test. Hope the data is still 
useful for you.

From vmstat for .32-rc6:
kswapd_highorder_rewakeup 8
kswapd_slept_prematurely_fast 329
kswapd_slept_prematurely_slow 55

From vmstat for .31.1:
kswapd_highorder_rewakeup 20
kswapd_slept_prematurely_fast 307
kswapd_slept_prematurely_slow 105

If you'd like me to test with the congestion_wait() revert on top of this 
for comparison, please let me know.

Cheers,
FJP

P.S. Your follow-up patch did not apply cleanly on top of the debug one as 
you seem to have made some changes between posting them (dropped kswapd_ 
from the sleeping_prematurely() function name and added a comment).