On Sun, 24 Oct 2004, Tom Lane wrote: > > Well, one really can't know without testing, but memory copies are > > extremely expensive if they go outside of the cache. > > Sure, but what about all the copying from write queue to page?
There's a pretty big difference between few-hundred-bytes-on-write and eight-kilobytes-with-every-read memory copy. As for the queue allocation, again, I have no data to back this up, but I don't think it would be as bad as BufMgrLock. Not every page will have a write queue, and a "hot" page is only going to get one once. (If a page has a write queue, you might as well leave it with the page after flushing it, and get rid of it only when the page leaves memory.) I see the OS issues related to mapping that much memory as a much bigger potential problem. cjs -- Curt Sampson <[EMAIL PROTECTED]> +81 90 7737 2974 http://www.NetBSD.org Make up enjoying your city life...produced by BIC CAMERA ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
