Re: Further reduction of bufmgr lock contention

Is this a TODO?

---------------------------------------------------------------------------

Tom Lane wrote:
> Josh Berkus <josh(at)agliodbs(dot)com> writes:
> > BTW, we're going to be testing this patch on Sun Niagara servers. What's
> > the outstanding bug with it? I don't quite follow.
>
> It's not acceptable as-is because of the risk of running out of shared
> memory for hashtable entries. In the existing code, there's a clear
> upper bound on the number of entries in the block-number-to-buffer hash
> table, ie, shared_buffers + 1 (the +1 because we acquire the new entry
> before releasing the old when reassigning a buffer). With multiple
> hashtables serving subsets of the buffers, the different tables might
> at different times need different numbers of entries, and that makes it
> a lot harder to be sure you won't run out of memory. I don't say it's
> insoluble, but the current patch wasn't even claimed to be safe by its
> author...
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
>

--
Bruce Momjian http://candle.pha.pa.us
EnterpriseDB http://www.enterprisedb.com

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