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Clean up WAL/buffer interactions as per my recent proposal. Get rid of the

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misleadingly-named WriteBuffer routine, and instead require routines that
change buffer pages to call MarkBufferDirty (which does exactly what it says).
We also require that they do so before calling XLogInsert; this takes care of
the synchronization requirement documented in SyncOneBuffer.  Note that
because bufmgr takes the buffer content lock (in shared mode) while writing
out any buffer, it doesn't matter whether MarkBufferDirty is executed before
the buffer content change is complete, so long as the content change is
completed before releasing exclusive lock on the buffer.  So it's OK to set
the dirtybit before we fill in the LSN.
This eliminates the former kluge of needing to set the dirtybit in LockBuffer.
Aside from making the code more transparent, we can also add some new
debugging assertions, in particular that the caller of MarkBufferDirty must
hold the buffer content lock, not merely a pin.
This commit is contained in:
Tom Lane
2006-03-31 23:32:07 +00:00
parent 89395bfa6f
commit a8b8f4db23
24 changed files with 434 additions and 537 deletions
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31
src/backend/commands/vacuumlazy.c
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@@ -31,7 +31,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.68 2006/03/05 15:58:25 momjian Exp $
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.69 2006/03/31 23:32:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -317,8 +317,8 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
lazy_record_free_space(vacrelstats, blkno,
PageGetFreeSpace(page));
}
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
WriteBuffer(buf);
MarkBufferDirty(buf);
UnlockReleaseBuffer(buf);
continue;
}
@@ -327,8 +327,7 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
empty_pages++;
lazy_record_free_space(vacrelstats, blkno,
PageGetFreeSpace(page));
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buf);
UnlockReleaseBuffer(buf);
continue;
}
@@ -439,12 +438,9 @@ lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,
if (hastup)
vacrelstats->nonempty_pages = blkno + 1;
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
if (pgchanged)
WriteBuffer(buf);
else
ReleaseBuffer(buf);
MarkBufferDirty(buf);
UnlockReleaseBuffer(buf);
}
/* save stats for use later */
@@ -524,8 +520,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
page = BufferGetPage(buf);
lazy_record_free_space(vacrelstats, tblk,
PageGetFreeSpace(page));
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
WriteBuffer(buf);
UnlockReleaseBuffer(buf);
npages++;
}
@@ -541,7 +536,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
* lazy_vacuum_page() -- free dead tuples on a page
* and repair its fragmentation.
*
* Caller is expected to handle reading, locking, and writing the buffer.
* Caller must hold pin and lock on the buffer.
*
* tupindex is the index in vacrelstats->dead_tuples of the first dead
* tuple for this page. We assume the rest follow sequentially.
@@ -557,6 +552,7 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
ItemId itemid;
START_CRIT_SECTION();
for (; tupindex < vacrelstats->num_dead_tuples; tupindex++)
{
BlockNumber tblk;
@@ -572,6 +568,8 @@ lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
uncnt = PageRepairFragmentation(page, unused);
MarkBufferDirty(buffer);
/* XLOG stuff */
if (!onerel->rd_istemp)
{
@@ -871,8 +869,7 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats)
if (PageIsNew(page) || PageIsEmpty(page))
{
/* PageIsNew probably shouldn't happen... */
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buf);
UnlockReleaseBuffer(buf);
continue;
}
@@ -928,9 +925,7 @@ count_nondeletable_pages(Relation onerel, LVRelStats *vacrelstats)
}
} /* scan along page */
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buf);
UnlockReleaseBuffer(buf);
/* Done scanning if we found a tuple here */
if (hastup)