2.6.6-1.435: kswapd clears out cache?

[Mike Fedyk]

Philip Molter wrote:
>> What type of workload does your application produce?
>>
>> Are you mounting and unmounting drives all of the time?  That can show 
>> the behaviour you're describing... Maybe you don't want the 
>> automounter turned on on your server.  Maybe you just need to set a 
>> longer timeout...
> 
> 
> No.
> 
> I actually also filed the same bug over at bugzilla.kernel.org and 
> Andrew Morton informs me that it has to do with the SMP/NUMA code and 
> the 4G/4G boundary.  By passing a mem=3936MB option to the kernel at 
> boot time, the problem with the filesystem cache getting wiped out goes 
> away.
> 
> Bug #2973 if anyone's interested in his explanation (which I don't do 
> justice since I'm not a kernel VM coder).

You really might want to turn on the swap.

In 2.4 you don't have the 4/4g split, and have a 1g/3g split.  That is a 
very different memory zone balancing situation than 4g/300MB you're 
running the 2.6 kernel under.

Unless you're happy with not using 300MB on your server...

Mike