Horton

Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: "Andrey M. Borodin" <x4mmm@yandex-team.ru>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-11-18T10:28:58Z
Lists: pgsql-hackers 
On Fri, Nov 17, 2023 at 6:16 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

Thanks for the review, all comments looks fine to me, replying to
those that need some clarification

> I wonder what's the deal with false sharing in the new
> bank_cur_lru_count array.  Maybe instead of using LWLockPadded for
> bank_locks, we should have a new struct, with both the LWLock and the
> LRU counter; then pad *that* to the cacheline size.  This way, both the
> lwlock and the counter come to the CPU running this code together.

Actually, the array lengths of both LWLock and the LRU counter are
different so I don't think we can move them to a common structure.
The length of the *buffer_locks array is equal to the number of slots,
the length of the *bank_locks array is Min (number_of_banks, 128), and
the length of the *bank_cur_lru_count array is number_of_banks.

> Looking at the coverage for this code,
> https://coverage.postgresql.org/src/backend/access/transam/clog.c.gcov.html#413
> it seems in our test suites we never hit the case where there is
> anything in the "nextidx" field for commit groups.  To be honest, I
> don't understand this group stuff, and so I'm doubly hesitant to go
> without any testing here.  Maybe it'd be possible to use Michael
> Paquier's injection points somehow?

Sorry, but I am not aware of "Michael Paquier's injection" Is it
something already in the repo? Can you redirect me to some of the
example test cases if we already have them? Then I will try it out.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Fix zeroing of pg_serial page without SLRU bank lock

  2. Fix misspelled assertions

  3. GUC table: Add description to computed variables

  4. Improve performance of subsystems on top of SLRU

  5. Rename SLRU elements in view pg_stat_slru

  6. Use atomic access for SlruShared->latest_page_number

  7. Split use of SerialSLRULock, creating SerialControlLock

  8. Index SLRUs by 64-bit integers rather than by 32-bit integers

  9. Add a macro templatized hashtable.