Received: from malur.postgresql.org ([217.196.149.56])
	by arkaria.postgresql.org with esmtp (Exim 4.84_2)
	(envelope-from <pgsql-committers-owner+archive@lists.postgresql.org>)
	id 1eJ2pa-0005qj-1M
	for pgsql-committers@arkaria.postgresql.org; Sun, 26 Nov 2017 19:43:10 +0000
Received: from localhost ([127.0.0.1] helo=malur.postgresql.org)
	by malur.postgresql.org with esmtp (Exim 4.84_2)
	(envelope-from <pgsql-committers-owner+archive@lists.postgresql.org>)
	id 1eJ2pY-0005av-D0
	for pgsql-committers@arkaria.postgresql.org; Sun, 26 Nov 2017 19:43:08 +0000
Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29])
	by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256)
	(Exim 4.84_2)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1eJ2pY-0005ak-8R
	for pgsql-committers@lists.postgresql.org; Sun, 26 Nov 2017 19:43:08 +0000
Received: from sss.pgh.pa.us ([66.207.139.130])
	by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256)
	(Exim 4.89)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1eJ2pQ-0005nM-PR
	for pgsql-committers@postgresql.org; Sun, 26 Nov 2017 19:43:07 +0000
Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1])
	by sss.pgh.pa.us (8.14.4/8.14.4) with ESMTP id vAQJgsqE031082;
	Sun, 26 Nov 2017 14:42:54 -0500
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Simon Riggs <simon@2ndquadrant.com>
cc: Andres Freund <andres@anarazel.de>, Tomas Vondra <tv@fuzzy.cz>,
        pgsql-committers <pgsql-committers@postgresql.org>
Subject: Re: pgsql: Generational memory allocator
In-reply-to: 
 <CANP8+jLbnDbd4ShH5B27Y0fRxDn3i=Zij3pNfp6u4LSSg66zDA@mail.gmail.com>
References: <E1eHa4J-0006hI-Q8@gemulon.postgresql.org>
 <20171123001649.y2nf7422iay6cw3v@alap3.anarazel.de>
 <CANP8+jKoT=Pg5W_3FcKiDf+FMrJhFYacxt_g5E0=tkmb5s8M6g@mail.gmail.com>
 <c903f275-2150-fa52-64bf-dca7b53ebf8d@fuzzy.cz>
 <16449.1511548313@sss.pgh.pa.us> <4618.1511573138@sss.pgh.pa.us>
 <bf84d940-90d4-de91-19dd-612e011007f4@fuzzy.cz>
 <6189.1511587105@sss.pgh.pa.us> <8991.1511639441@sss.pgh.pa.us>
 <20171125200014.qbewtip5oydqsklt@alap3.anarazel.de>
 <21466.1511644760@sss.pgh.pa.us> <2875.1511646362@sss.pgh.pa.us>
 <CANP8+jKRt0Yenw8Ln4J4u=UsDVkCBgPmjDE2buYou-H9VTMZjw@mail.gmail.com>
 <16797.1511718406@sss.pgh.pa.us>
 <CANP8+jKCX0sTqR8ZexTMxr03Eu3wsuwV2qit0EB0TVorMeSXBg@mail.gmail.com>
 <28144.1511722417@sss.pgh.pa.us>
 <CANP8+jLbnDbd4ShH5B27Y0fRxDn3i=Zij3pNfp6u4LSSg66zDA@mail.gmail.com>
Comments: In-reply-to Simon Riggs <simon@2ndquadrant.com>
	message dated "Mon, 27 Nov 2017 06:09:02 +1100"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <31080.1511725374.1@sss.pgh.pa.us>
Date: Sun, 26 Nov 2017 14:42:54 -0500
Message-ID: <31081.1511725374@sss.pgh.pa.us>
List-Id: <pgsql-committers.lists.postgresql.org>
List-Help: <https://lists.postgresql.org/manage/>
List-Subscribe: <https://lists.postgresql.org/manage/>
List-Post: <mailto:pgsql-committers@lists.postgresql.org>
List-Owner: <mailto:pgsql-committers-owner@lists.postgresql.org>
List-Archive: <https://www.postgresql.org/list/pgsql-committers>
Precedence: bulk

Simon Riggs <simon@2ndquadrant.com> writes:
> On 27 November 2017 at 05:53, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Well, let's not overthink this, because anything under 8K is going to
>> be rounded up to the next power of 2 anyway by aset.c.  Based on this
>> point I'd say that BLCKSZ/2 or BLCKSZ/4 would be reasonable candidates
>> for the minimum.

> BLCKSZ/2 seems best then.

Sold, will make it so.

> I guess that means palloc doesn't work well with BLCKSZ > 8192

Don't think it's particularly related.

			regards, tom lane