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From: Andrey Borodin <[email protected]>
To: Thomas Munro <[email protected]>
Cc: Gilles Darold <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Alexander Korotkov <[email protected]>
Cc: Anastasia Lubennikova <[email protected]>
Cc: Daniel Gustafsson <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: MultiXact\SLRU buffers configuration
Date: Fri, 26 Mar 2021 20:52:22 +0500
Message-ID: <[email protected]> (raw)
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> 26 марта 2021 г., в 11:00, Andrey Borodin <[email protected]> написал(а):
> 
>> I'm not saying the 0002 patch is bug-free yet though, it's a bit finickity.
> I think the idea of speeding up linear search is really really good for scaling SLRUs. It's not even about improving normal performance of the cluster, but it's important from preventing pathological degradation under certain circumstances. Bigger cache really saves SLAs :) I'll look into the patch more closely this weekend. Thank you!


Some thoughts on HashTable patch:
1. Can we allocate bigger hashtable to reduce probability of collisions?
2. Can we use specialised hashtable for this case? I'm afraid hash_search() does comparable number of CPU cycles as simple cycle from 0 to 128. We could inline everything and avoid hashp->hash(keyPtr, hashp->keysize) call. I'm not insisting on special hash though, just an idea.
3. pageno in SlruMappingTableEntry seems to be unused.

Thanks!

Best regards, Andrey Borodin.




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