Re: Load distributed checkpoint

> (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