bg-writer queries regarding ( [Testperf-general] BufferSync and bgwriter )

browsing through the archives i came across this::
http://pgfoundry.org/pipermail/testperf-general/2004-December/000080.html

which seems to be of the time when bgwriter was in development stage....

i need some clarifications......

is there a separate list of dirty buffers and clean buffers.....

if there is then its ok.... bgwriter will start from LRU side and keep writing till it has written either bgwriter_maxpages or bgwriter_percent....

now if there is no separate list for dirty buffers.... bgwriter will scan the entire list to check how many are there.... which it needs for bgwriter_percent... and then write bgwriter_maxpages or bgwriter_percent pages... which ever is less....

also how should we decide wht should be the bgwriter settings.... is there a way to determine how many dirty buffers are there currently...

should i check the io usage...and if its free increase bgwriter and if its full reduce it.... which tool should i use for determining the io-usage....

regards
himanshu

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