Gregory Stark wrote:
"Heikki Linnakangas" <[EMAIL PROTECTED]> writes:
One problem is that you have to atomically update the visibility map when
you update the heap. That means that you have to lock the visibility map
page and the heap page at the same time. If the visibility map is in the
heap, you need to take care that you don't deadlock.
Well that's still a problem if it's in another filenode.
On the other hand if you allocate a whole byte to every page you could set it
atomically and not have to lock the page. Effectively having the lock on the
original page protect the info byte. Whereas setting a single bit requires
protecting against someone setting one of the other bits corresponding to
another page entirely.
I don't buy that. I believe at least on some architectures you'd get a
word-long load+modify+store, and scribble the neighboring bytes.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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