> We're seeing an average of 30,000 context-switches a sec. This problem > was much worse w/8.0 and got bearable with 8.1 but slowly resurfaced. Is this from LWLock or spinlock contention? strace'ing a few backends could tell the difference: look to see how many select(0,...) you see compared to semop()s. Also, how many of these compared to real work (such as read/write calls)? Do you have any long-running transactions, and if so does shutting them down help? There's been some discussion about thrashing of the pg_subtrans buffers being a problem, and that's mainly a function of the age of the oldest open transaction. regards, tom lane
