Jan Wieck <[EMAIL PROTECTED]> writes: > This all only holds water, if the OS is allowed to swap out shared > memory. And that was my initial question, how likely is it to find this > to be true these days?
I think it's more likely that not that the OS will consider shared memory to be potentially swappable. On some platforms there is a shmctl call you can make to lock your shmem in memory, but (a) we don't use it and (b) it may well require privileges we haven't got anyway. This has always been one of the arguments against making shared_buffers really large, of course --- if the buffers aren't all heavily used, and the OS decides to swap them to disk, you are worse off than you would have been with a smaller shared_buffers setting. However, I'm still really nervous about the idea of using effective_cache_size to control the ARC algorithm. That number is usually entirely bogus. Right now it is only a second-order influence on certain planner estimates, and I am afraid to rely on it any more heavily than that. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org