Re: [PATCHES] update i386 spinlock for hyperthreading

Tom Lane wrote:

>Bruce Momjian <pgman@candle.pha.pa.us> writes:
>  
>
>>Manfred Spraul wrote:
>>    
>>
>>>I remember there were patches that tried other algorithms instead of the 
>>>simple LRU for the buffer manager. Has anyone tried to change the 
>>>locking of the buffer manager?
>>>      
>>>
>
>  
>
>>CVS HEAD already has an Adaptive Replacement Cache (ARC) for buffer
>>replacement.
>>    
>>
>
>That's irrelevant to the problem, though.  Unless the ARC code uses data
>structures that are more amenable to localized locking than the old
>global buffer freelist.  (Jan?)
>
>            regards, tom lane
>  
>

Not that I know of. The new strategy uses one shared hash table like the 
old, and one buffer pool as well. It grabs the same old Bufmgr lock 
during the lookup+replacement decision process, gives it up during 
eventual IO, grabs it again when done with the IO. As a matter of fact, 
the strategy itself does no locking at all. Like the old LRU code it 
simply assumes that the buffer manager holds the lock during calls.


Jan

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