Horton

Re: MultiXact\SLRU buffers configuration

x4mmm@yandex-team.ru

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From: Andrey Borodin <x4mmm@yandex-team.ru>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Gilles Darold <gilles@darold.net>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alexander Korotkov <aekorotkov@gmail.com>, Anastasia Lubennikova <a.lubennikova@postgrespro.ru>, Daniel Gustafsson <daniel@yesql.se>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-03-26T15:52:22Z
Lists: pgsql-hackers 

> 26 марта 2021 г., в 11:00, Andrey Borodin <x4mmm@yandex-team.ru> 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.

Commits

  1. Rework new SLRU test with injection points

  2. injection_point: Add injection_points.stats

  3. injection_points: Add initialization of shmem state when loading module

  4. Add injection-point test for new multixact CV usage

  5. Use conditional variable to wait for next MultiXact offset

  6. Improve performance of subsystems on top of SLRU

  7. Adjust VACUUM hastup LP_REDIRECT comments.

  8. Test replay of regression tests, attempt II.