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Fix capitalization in README.

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Vik Fearing
This commit is contained in:
Robert Haas 2014-02-17 14:02:10 -05:00
parent e7f409756d
commit 876f78d575
1 changed files with 7 additions and 7 deletions
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14
src/backend/storage/buffer/README
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@ -176,8 +176,8 @@ small limit value) whenever the buffer is pinned. (This requires only the
buffer header spinlock, which would have to be taken anyway to increment the buffer header spinlock, which would have to be taken anyway to increment the
buffer reference count, so it's nearly free.) buffer reference count, so it's nearly free.)
The "clock hand" is a buffer index, NextVictimBuffer, that moves circularly The "clock hand" is a buffer index, nextVictimBuffer, that moves circularly
through all the available buffers. NextVictimBuffer is protected by the through all the available buffers. nextVictimBuffer is protected by the
BufFreelistLock. BufFreelistLock.
The algorithm for a process that needs to obtain a victim buffer is: The algorithm for a process that needs to obtain a victim buffer is:
@ -189,8 +189,8 @@ is pinned or has a nonzero usage count, it cannot be used; ignore it and
return to the start of step 2. Otherwise, pin the buffer, release return to the start of step 2. Otherwise, pin the buffer, release
BufFreelistLock, and return the buffer. BufFreelistLock, and return the buffer.
3. Otherwise, select the buffer pointed to by NextVictimBuffer, and 3. Otherwise, select the buffer pointed to by nextVictimBuffer, and
circularly advance NextVictimBuffer for next time. circularly advance nextVictimBuffer for next time.
4. If the selected buffer is pinned or has a nonzero usage count, it cannot 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 be used. Decrement its usage count (if nonzero) and return to step 3 to
@ -254,11 +254,11 @@ Background Writer's Processing
The background writer is designed to write out pages that are likely to be The background writer is designed to write out pages that are likely to be
recycled soon, thereby offloading the writing work from active backends. recycled soon, thereby offloading the writing work from active backends.
To do this, it scans forward circularly from the current position of 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, dirty and not pinned nor marked with a positive usage count. It pins,
writes, and releases any such buffer. 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 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 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 enough to check the dirtybit. Even without that assumption, the writer
@ -268,7 +268,7 @@ the contention cost of the writer compared to PG 8.0.)
During a checkpoint, the writer's strategy must be to write every dirty 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 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. ones that backends might otherwise have to write for themselves soon.
The background writer takes shared content lock on a buffer while writing it The background writer takes shared content lock on a buffer while writing it