From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
Cc: | Jakub Glapa <jakub(dot)glapa(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Fabio Isabettini <fisabettini(at)voipfuture(dot)com>, Arne Roland <A(dot)Roland(at)index(dot)de>, Sand Stone <sand(dot)m(dot)stone(at)gmail(dot)com>, Rick Otten <rottenwindfish(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: dsa_allocate() faliure |
Date: | 2019-02-10 06:40:52 |
Message-ID: | CA+TgmoY4t7r9ac2vRnX1grL7yAaN9hJK6kG_8-D6ro8hNNjz-w@mail.gmail.com |
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Lists: | pgsql-hackers pgsql-performance |
On Sun, Feb 10, 2019 at 2:37 AM Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> ... but why would it do that? I can reproduce cases where (for
> example) FreePageManagerPutInternal() returns 179, and then
> FreePageManagerLargestContiguous() returns 179, but then after
> FreePageBtreeCleanup() it returns 178. At that point FreePageDump()
> says:
>
> btree depth 1:
> 77(at)0 l: 27(1) 78(178)
> freelists:
> 1: 27
> 129: 78(178)
>
> But at first glance it shouldn't be allocating pages, because it just
> does consolidation to try to convert to singleton format, and then it
> does recycle list cleanup using soft=true so that no allocation of
> btree pages should occur.
I think I see what's happening. At the moment the problem occurs,
there is no btree - there is only a singleton range. So
FreePageManagerInternal() takes the fpm->btree_depth == 0 branch and
then ends up in the section with the comment /* Not contiguous; we
need to initialize the btree. */. And that section, sadly, does not
respect the 'soft' flag, so kaboom. Something like the attached might
fix it.
Boy, I love FreePageManagerDump!
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
Attachment | Content-Type | Size |
---|---|---|
dsa-allocate-btree-init-soft.patch | application/octet-stream | 598 bytes |
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