Bruce Momjian wrote:
> Jan Wieck wrote:
>> >> 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
>
> The above line is the one I was asking about? Does that just control
> debug output interval? If so, it should be named more appropriately.
Yes, all it controls is the DEBUG1 output eveny N seconds. What is
inappropriate about it? It is exactly that, it shows the sizes and
recent hit rates for the 4 different CDB queues of the strategy. Have a
better one?
The output is not really of any use yet. The background writer though
will add a third line to this output, the number of clean buffers in
front of the T1 and T2 queues. That will be the #1 tool for adjusting
the background writer parameters so that it keeps the cache clean enough
that backends don't need to write, and dirty enough that high frequently
used blocks don't get written too often.
>
>> >>
>> >> 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
>
> No, I don't see much value to this and would encourage people to play
> with something that probably is is of little value.
Me neither, just wanted to have asked.
Jan
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