On 01.10.2012 19:49, pg noob wrote:
Hi all, I have a question about the deadlock_timeout in regards to performance. Right now we have this timeout set at its default of 1s. My understanding of it is that this means that every 1 second the server will check for deadlocks.
Not quite. It means that when a backend gets blocked, waiting on a lock, it will check for deadlocks after waiting for 1 second. When no backend is waiting for a lock, there are no deadlock checks regardless of deadlock_timeout.
What I am wondering is how much of a performance improvement we would expect to get if this was raised to 30 seconds? Is it negligible or could it be a substantial performance improvement on a busy system? We very rarely have deadlocks and waiting 30 seconds to discover one doesn't seem too bad.
It's almost certainly negligible. If you regularly have deadlocks, it might even better for performance to make the timeout shorter than 1 s, so that deadlocks are detected earlier, and backends will spend less time deadlocked, and more time doing real work. Although I doubt it will make any meaningful difference either way.
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