Subject: Re: PATCH: two slab-like memory allocators
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>,
 Andres Freund <andres@anarazel.de>
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Cc: Robert Haas <robertmhaas@gmail.com>, John Gorman <johngorman2@gmail.com>,
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From: Petr Jelinek <petr@2ndquadrant.com>
Message-ID: <9cdbe694-1b49-0c61-b0b2-d95ef2b3cb31@2ndquadrant.com>
Date: Sun, 27 Nov 2016 19:25:17 +0100
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On 15/11/16 01:44, Tomas Vondra wrote:
> Attached is v6 of the patch series, fixing most of the points:
> 
> * common bits (valgrind/randomization/wipe) moved to memdebug.h/c
> 
> Instead of introducing a new header file, I've added the prototypes to
> memdebug.h (which was already used for the valgrind stuff anyway), and
> the implementations to a new memdebug.c file. Not sure what you meant by
> "static inlines" though.

I think Andres wanted to put the implementation to the static inline
functions directly in the header (see parts of pg_list or how atomics
work), but I guess you way works too.

> 
> I've however kept SlabContext->freelist as an array, because there may
> be many blocks with the same number of free chunks, in which case moving
> the block in the list would be expensive. This way it's simply
> dlist_delete + dlist_push.
> 

+1

I get mxact isolation test failures in test_decoding with this version
of patch:
  step s0w: INSERT INTO do_write DEFAULT VALUES;
+ WARNING:  problem in slab TXN: number of free chunks 33 in block
0x22beba0 does not match bitmap 34
  step s0start: SELECT data FROM
pg_logical_slot_get_changes('isolation_slot', NULL, NULL,
'include-xids', 'false');
  data
and
  step s0alter: ALTER TABLE do_write ADD column ts timestamptz;
  step s0w: INSERT INTO do_write DEFAULT VALUES;
+ WARNING:  problem in slab TXN: number of free chunks 33 in block
0x227c3f0 does not match bitmap 34
  step s0start: SELECT data FROM
pg_logical_slot_get_changes('isolation_slot', NULL, NULL,
'include-xids', 'false');
  data


Also, let's just rename the Gen to Generation.

-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services


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