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Premature and/or over-optimization is often claimed to be a root of most evil in the programming world. However, what to do when optimization IS neccessary?

IT Hares discuss certain not-so-trivial optimization techniques. It doesn’t mean that you should use them at all costs (and most likely, you don’t); however, if you do have a reason to optimize – this information may be handy.

Optimizations, page 1:

OLTP DB Optimizations 102 – Group Commits

Quote: “if we can commit several transactions at the same time – RDBMS needs to fsync() our DB logs to physical disks only once”
Another Quote: “if going our preferred way of single-writing-DB connection – make sure NOT to use RDBMS-level Group Com”

OLTP DB Optimizations 102 –100% Coherent App-Level Cache for Single-writing-DB-connection

Quote: “with our app-level cache, we’re guaranteed to get exactly the same results as if we’d be querying the underlying database.”
Another Quote: “why settle for invalidation when we can modify cache accordingly, saving on the extra DB request when we’re dealing with the same USER again?”

Allocator for (Re)Actors with Optional Kinda-Safety and Relocation

Quote: “‘Safe with relocation’ mode will allow us to eliminate dreaded ‘external fragmentation’ – which tends to cause quite a bit of trouble for long-running systems”
Another Quote: “For a long while, I have been a strong proponent of message-passing mechanisms over mutex-based thread sync for concurrency purposes”

Ultra-fast Serialization of C++ Objects

Quote: “in both these cases we can be 100% sure that we’ll be deserializing this state on the executable which is identical to the executable which serialized the state.”
Another Quote: “Even when comparing with home-grown code with per-field serialization, our Ultra-Fast Serialization still wins (up to 1.5x-2x) “

Some Big-Os are Bigger Than Others

Quote: “Strictly speaking, for real-world computers, every algorithm which completes in a finite time can be said to be O(1)
Another Quote: “now the difference because of unfortunate ‘jumps’ over (uncached at the time) memory can lead to a 100x+ (!) performance difference. However, it is still O(1) and is rarely taken into account during performance analysis”