I recently noticed that transfer speeds with samba(exclusively, even with loopback - iperf works just fine) have dropped to around 5MB/s on my gigabit network. Before it could easily reach 70MB/s and beyond.
I actually wrote a long description of the problem here but then decided to double-check everything and noticed that htop reports 100% RAM usage and most of the bar was yellow, e.g. reserved for cache.
After clearing the cache with
sync; echo 3 > /proc/sys/vm/drop_caches (found at http://www.hosting.com/support/linux/clear-memory-cache-on-linux-server), transfer speeds immediately went from the 5MB/s to 50MB/s.
I'm being told that Linux manages its memory efficiently and I think using spare RAM to speed up disk access is great, so I'm suspecting there's something wrong with my configuration. Is this the case or is this a samba/linux quirk?
I'm using samba 3.6.6 on Ubuntu 12.10.