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Re: CheckpointStartLock starvation

From: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: CheckpointStartLock starvation
Date: 2007-04-03 00:52:32
Message-ID: 20070403094025.C156.ITAGAKI.TAKAHIRO@oss.ntt.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackers
Heikki Linnakangas <heikki(at)enterprisedb(dot)com> wrote:

> It looks like the bgwriter gets starved waiting on the 
> CheckpointStartLock. The CheckpointStartLock is held in shared mode over 
> an XLogFlush when committing, which on an extremely busy system like a 
> benchmark is always long enough to have a new transaction to acquire the 
> CheckpointStartLock again.

If the starvation comes from giving unfair priorities on shared locks
against exclusive locks, does the below TODO item help us?

| Locking
| Fix priority ordering of read and write light-weight locks (Neil) 
| http://archives.postgresql.org/pgsql-hackers/2004-11/msg00893.php
| http://archives.postgresql.org/pgsql-hackers/2004-11/msg00905.php 

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center



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