Lindsay Holmwood is the lead developer behind Visage. He started off with a use case that a web server is having some intermittent problems. It's about collecting metrics of the servers. He mentioned sysstat, dstat,sar, top, etc. But it's hard to correlate the data.
Simon Lyall said with a typical LAMP stack you can get 5 to 10 hits a second. He suggested if you add a data cache (caching of DB queries) you can get upto 100 h/s. If you add a page cache you can get upto about 300 h/s. To get way up from there you need big infrastructure with load balancing.
Steven Ellis is talking about cgroups. CGroups are about an in kernel feature and userspace tools and librarys to manage how resources are allocated to users and processes. Resources are disk, network and CPU.
Shoaib Mir is talking about performance of postgresql, and how to tune it. He started with application analysis. How do you work out if it's reading large amounts of data, or writing, or doing complicated queries.
Mark Suter talked about their implementation of a secure gateway. They protect networks that have servers hat have low security efforts. They do firewall, IDS/IPS, router and switch administration, Linux adminstration, external hosting infrastructure, Web XML messaging gateways. His company has some kind of certification with their managed stuff (and if they loose certification they'll loose some of their big contracts).