Mark Wong wrote:
Pretty, simple. One to load the database, and 1 to query it. I'll attach them.I've tested it on my dual-cpu computer:
- it works, both cpus run within the postmaster. It seems something your gentoo setup is broken.
- the number of context switch is down slightly, but not significantly: The glibc implementation is more or less identical to the implementation right now in lwlock.c: a spinlock that protects a few variables that are used to implement the actual mutex, several wait queues: one for spinlock busy, one or two for the actual mutex code.
Around 25% of the context switches are from spinlock collisions, the rest are from actual mutex collisions. It might be possible to get rid of the spinlock collisions by writing a special, futex based semaphore function that only supports exclusive access [like sem_wait/sem_post], but I don't think that it's worth the effort: 75% of the context switches would remain.
What's needed is a buffer manager that can do lookups without a global lock.
-- Manfred
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