This has been saved for the 8.4 release:


Greg Smith wrote:
> I'm mostly done with my review of the "Automatic adjustment of 
> bgwriter_lru_maxpages" patch.  In addition to issues already brought up 
> with that code, there are some small things that need to be done to merge 
> it with the recent pg_stat_bgwriter patch, and I have some concerns about 
> its unbounded scanning of the buffer pool; I'll write that up in more 
> detail or just submit an improved patch as I get time this week.
> But there's a fundamental question that has been bugging me, and I think 
> it impacts the direction that code should take.  Unless I'm missing 
> something in my reading, buffers written out by the LRU writer aren't ever 
> put onto the free list.  I assume this is to stop from prematurely 
> removing buffers that contain useful data.  In cases where a substantial 
> percentage of the buffer cache is dirty, the LRU writer has to scan a 
> significant portion of the pool looking for one of the rare clean buffers, 
> then write it out.  When a client goes to grab a free buffer afterward, it 
> has to scan the same section of the pool to find the now clean buffer, 
> which seems redundant.
> With the new patch, the LRU writer is fairly well bounded in that it 
> doesn't write out more than it thinks it will need; you shouldn't get into 
> a situation where many more pages are written than will be used in the 
> near future.  Given that mindset, shouldn't pages the LRU scan writes just 
> get moved onto the free list?
> --
> * Greg Smith [EMAIL PROTECTED] Baltimore, MD
> ---------------------------(end of broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings

  Bruce Momjian  <[EMAIL PROTECTED]>

  + If your life is a hard drive, Christ can be your backup. +

---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
       subscribe-nomail command to [EMAIL PROTECTED] so that your
       message can get through to the mailing list cleanly

Reply via email to