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Re: Load distributed checkpoint

From: "Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
To: "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Load distributed checkpoint
Date: 2006-12-22 11:08:55
Message-ID: 02e401c725b9$91fb9530$19527c0a@OPERAO (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
> (3) is very strange. Your machine seems to be too restricted
> by WAL so that other factors cannot be measured properly.

Right... It takes as long as 15 seconds to fsync 1GB file.  It's
strange.  This is a borrowed PC server, so the disk may be RAID 5?
However, the WAL disk and DB  disks show the same throughput.  I'll
investigate.  I may have to find another machine.

- Pentium4 3.6GHz with HT / 3GB RAM / Windows XP :-)

Oh, Windows.  Maybe the fsync() problem Itagaki-san pointed out does
not exist.
BTW, your env is showing attractive result, isn't it?

----- Original Message ----- 
From: "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
To: "Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Sent: Friday, December 22, 2006 6:09 PM
Subject: Re: [HACKERS] Load distributed checkpoint


"Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:

> (1) Default case(this is show again for comparison and reminder)
> 235  80  226  77  240
> (2) Default + WAL 1MB case
> 302  328  82  330  85
> (3) Default + wal_sync_method=open_sync case
> 162  67  176  67  164
> (4) (2)+(3) case
> 322  350  85  321  84
> (5) (4) + /proc/sys/vm/dirty* tuning
> 308  349  84  349  84

(3) is very strange. Your machine seems to be too restricted
by WAL so that other factors cannot be measured properly.


I'll send results on my machine.

- Pentium4 3.6GHz with HT / 3GB RAM / Windows XP :-)
- shared_buffers=1GB
- wal_sync_method = open_datasync
- wal_buffers = 1MB
- checkpoint_segments = 16
- checkpoint_timeout = 5min

I repeated "pgbench -c16 -t500 -s50"
and picked up results around checkpoints.

[HEAD]
...
560.8
373.5 <- checkpoint is here
570.8
...

[with patch]
...
562.0
528.4 <- checkpoint (fsync) is here
547.0
...

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





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