"Tom Lane" <[EMAIL PROTECTED]> writes: > I don't really see why it's "overkill".
Well I think it may be overkill in that we'll be writing out buffers that still have a decent chance of being hit again. Effectively what we'll be doing in the approximated LRU queue is writing out any buffer that reaches the 80% point down the list. Even if it later gets hit and pulled up to the head again. I suppose that's not wrong though, the whole idea of the clock sweep is that that's precisely the level of precision to which it makes sense to approximate the LRU. Ie, that any point in the top 20% is equivalent to any other and when we use a buffer we want to promote it to somewhere "near" the head but any point in the top 20% is good enough. Then any point in the last 20% should be effectively "good enough" too be considered a target buffer to clean as well. If we find it's overkill then what we should consider doing is raising BM_MAX_USAGE_COUNT. That's effectively tuning the percentage of the lru chain that we decide we try to keep clean. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
