buffer header spinlock, which would have to be taken anyway to increment the
buffer reference count, so it's nearly free.)
-The "clock hand" is a buffer index, NextVictimBuffer, that moves circularly
-through all the available buffers. NextVictimBuffer is protected by the
+The "clock hand" is a buffer index, nextVictimBuffer, that moves circularly
+through all the available buffers. nextVictimBuffer is protected by the
BufFreelistLock.
The algorithm for a process that needs to obtain a victim buffer is:
return to the start of step 2. Otherwise, pin the buffer, release
BufFreelistLock, and return the buffer.
-3. Otherwise, select the buffer pointed to by NextVictimBuffer, and
-circularly advance NextVictimBuffer for next time.
+3. Otherwise, select the buffer pointed to by nextVictimBuffer, and
+circularly advance nextVictimBuffer for next time.
4. If the selected buffer is pinned or has a nonzero usage count, it cannot
be used. Decrement its usage count (if nonzero) and return to step 3 to
The background writer is designed to write out pages that are likely to be
recycled soon, thereby offloading the writing work from active backends.
To do this, it scans forward circularly from the current position of
-NextVictimBuffer (which it does not change!), looking for buffers that are
+nextVictimBuffer (which it does not change!), looking for buffers that are
dirty and not pinned nor marked with a positive usage count. It pins,
writes, and releases any such buffer.
-If we can assume that reading NextVictimBuffer is an atomic action, then
+If we can assume that reading nextVictimBuffer is an atomic action, then
the writer doesn't even need to take the BufFreelistLock in order to look
for buffers to write; it needs only to spinlock each buffer header for long
enough to check the dirtybit. Even without that assumption, the writer
During a checkpoint, the writer's strategy must be to write every dirty
buffer (pinned or not!). We may as well make it start this scan from
-NextVictimBuffer, however, so that the first-to-be-written pages are the
+nextVictimBuffer, however, so that the first-to-be-written pages are the
ones that backends might otherwise have to write for themselves soon.
The background writer takes shared content lock on a buffer while writing it
projects / postgresql / commitdiff