> We have an 2 x quad core server with 32 gb ram. If many clients > connect to this server (only memcached runs on it) the first core run > to nearly 100 % use by si (software interrups) and so some client > can't reach the server. > Memcached runs currently with 4 threads and with version (1.4.2). All > other cores have 70 % idle so I ask me is there a possibility to > improve the performance? >
This is an issue with how your network interrupts are being routed, not with how memcached is being threaded. Wish I had some good links offhand for this, because it's a little obscure to deal with. In short; you'll want to balance your network interrupts across cores. Google for blog posts about smp_affinity for network cards and irqbalance (which poorly tries to automatically do this). Depending on how many NIC's you have and if it's multiqueued or not you'll have to tune it differently. Linux 2.6.35 has some features for extending the speed of single-queued NIC's (find the pages discussing it on kernelnewbies.org).
