Re: cvs head? initdb? - Mailing list pgsql-hackers

Robert Treat wrote:

> On Fri, 2003-11-14 at 10:32, Jan Wieck wrote:
>> Bruce Momjian wrote:
>> > Jan Wieck wrote:
>> >> Christopher Browne wrote:
>> >> 
>> >> > elein@varlena.com (elein) writes:
>> >> >> What is the status of CVS head?  Isn't it in sync with 7.4.RC2?  I
>> >> >> just upgraded from CVS and rebuilt clean and initdb now gives this
>> >> >> lovely informative initdb failed message.
>> >> > 
>> >> > No, I believe that they have started applying 7.5 patches, notably
>> >> > including reimplementing initdb in C.
>> >> > 
>> >> > Jan checked in the ARC changes last night, and he and Tom ran into
>> >> > some problems, leading to that being pulled back out, while he
>> >> > revisits the code.
>> >> 
>> >> Yeah, there was a problem with *extreme* sharing ... the code tried to 
>> >> use the same buffer for multiple disk blocks at the same time, and 
>> >> somehow the backends did not agree on the correct content. But it's 
>> >> fixed and back in. You can see ARC working by setting
>> >> 
>> >>      buffer_strategy_status_interval = 10 # seconds
>> >> 
>> >> and starting postmaster with -d1
>> > 
>> > It is not on by default?
>> > 
>> 
>> Sure not. Why would someone turn on debug messages by default?
>> 
>> Or did you mean ARC itself? Since it replaced the old LRU code, it is 
>> the only choice you have now. Which sort of raises the question if we 
>> would want to have multiple choices, like a config option
>> 
>> buffer_replacement_strategy = lru|lru2|arc
>> 
> 
> people would always want to have those choices (especially for doing
> development/testing/benchmarking between the different methods) the
> question is is it worth the effort to give people those options?

And in the case of the cache strategy, the point is that different 
access patterns might be served better by different strategies. Then 
again, who will really test this and try to tune ALL of them to find the 
best choice, and is this possible at all given that all databases under 
one postmaster share the same buffer pool?


Jan


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