Is there a TODO here? ---------------------------------------------------------------------------
Tom Lane wrote: > Neil Conway <[EMAIL PROTECTED]> writes: > > In the BufferDesc struct, there seem to be two ways to mark a buffer > > page as dirty: setting the BM_DIRTY bit mask in the 'flags' field of the > > struct, and setting the 'cntxDirty' field to true. What is the > > difference between these two indications of a page's dirtiness? > > Or, more to the point, is there a reason we have two ways to do what > > looks like the same thing? > > I believe the reason for this is that you are allowed to set cntxDirty > to TRUE while holding (only) the context lock on the buffer, while > messing with the buffer flags word requires holding (only) the > BufMgrLock. Getting rid of cntxDirty would mean additional grabbings of > the BufMgrLock when we want to mark buffers dirty. > > The real solution to this is probably to rethink the rules for locking > in the buffer manager. I've thought for some time that the BufMgrLock is > a system-wide bottleneck; if we could replace it by finer-grain locks, > and in particular use the per-buffer locks for operations affecting just > the state of a single buffer, we'd be ahead of the game. > > > BTW, I'd like to remove the behavior that LockBuffer(buf, EXCLUSIVE) > > automatically marks the page as dirty. > > Yeah. This has been discussed before, see the archives: > http://archives.postgresql.org/pgsql-hackers/2002-11/msg00488.php > http://archives.postgresql.org/pgsql-hackers/2002-11/msg00679.php > http://archives.postgresql.org/pgsql-hackers/2002-11/msg00512.php > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 8: explain analyze is your friend > -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
