1.) NEEDINFO: pagecache

RHEL6 does no have the /proc/sys/vm/pagecache tunable parameter.

2.) NEEDINFO: slabcache

Not sure what this means, there is no slabcache file in the /proc filesystem.

3.) min_free_kbytes

Be cautious when setting this parameter, as both too-low and too-high values can be damaging.
Setting it to a value lower than 1024 KB results in a system that is prone to deadlock under high loads. A reason for this would be nice.
However, setting this parameter to a value that is too high will cause your system to become out-of-memory immediately. I assume "too high" is "as much/more memory than your system has available". 

Setting min_free_kbytes too low will prevent the system from reclaiming memory all together.  This can result in system hangs and/or OOM killing several processes.

Too high is something like 5% - 10% of memory.  Linux is designed to use all of the RAM to cache filesystem data, setting min_free_kbytes higher than that will cause the system to spend all of its time reclaiming memory.

4.) drop_caches
    Is this the right parameter to use with page cache and slab cache? The pagecache parameter doesn't seem to exist any more. 

/sys/proc/vm/drop_caches does exist in RHEL6.  

"echo 1 > /proc/sys/vm/drop_caches" will cause to the system to invalidate and free all pagecache memory.

"echo 2 > /proc/sys/vm/drop_caches" will cause the system to free all unused slabcache memory.

"echo 3 > /proc/sys/vm/drop_caches" cause the system to free both pagecache and slabcache memory.

The use of /proc/sys/vm/slabcache should be limited to freeinf memory between benchmarking runs and should not be used in a production environment.


Larry

ACK to the VM tuning chapter.

Larry