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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: Thu, 8 Apr 2021 10:24:55 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+hUKGLCLDtgDj2Xsf0uBk5WXDCeHxBDDJPsyY7m65Fde-=pyg@mail.gmail.com>
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> 8 апр. 2021 г., в 03:30, Thomas Munro <[email protected]> написал(а):
> 
> Here's another approach that is a little less exciting than
> "tournament RR" (or whatever that should be called; I couldn't find an
> established name for it).  This version is just our traditional linear
> search, except that it stops at 128, and remembers where to start from
> next time (like a sort of Fisher-Price GCLOCK hand).  This feels more
> committable to me.  You can argue that all buffers above 128 are bonus
> buffers that PostgreSQL 13 didn't have, so the fact that we can no
> longer find the globally least recently used page when you set
> xact_buffers > 128 doesn't seem too bad to me, as an incremental step
> (but to be clear, of course we can do better than this with more work
> in later releases).
I agree that this version of eviction seems much more effective and less intrusive than RR. And it's still LRU, which is important for subsystem that is called SLRU.
shared->search_slotno is initialized implicitly with memset(). But this seems like a common practice.
Also comment above "max_search = Min(shared->num_slots, MAX_REPLACEMENT_SEARCH);" does not reflect changes.

Besides this patch looks good to me.

Thanks!

Best regards, Andrey Borodin.

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