Re: PANIC caused by open_sync on Linux

From: ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>
To: Greg Smith <gsmith(at)gregsmith(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: PANIC caused by open_sync on Linux
Date: 2007-10-29 01:03:59
Message-ID: 20071029095034.62BE.ITAGAKI.TAKAHIRO@oss.ntt.co.jp
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Greg Smith <gsmith(at)gregsmith(dot)com> wrote:

> There's a couple of potential to-do list ideas that build on the changes
> in this area in 8.3:
>
> -Aggressively pre-allocate WAL segments
> -Space out checkpoint fsync requests in addition to disk writes
> -Consider re-inserting a smarter bgwriter all-scan that writes sorted by
> usage count during idle periods

I'd like to add:
- Remove "filling with zero" before we recycle WAL segments.

If it is not needed, we can avoid buffered i/o on open_sync except
first allocation of segments. I think we can do it if we have more
robust WAL records that can ignore garbage data written before.

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

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