From: Qingqing Zhou <zhouqq@cs.toronto.edu>
To: pgsql-hackers@postgresql.org
Subject: Re: ice-broker scan thread
Date: Tue, 29 Nov 2005 00:09:11 -0500
Message-ID: <dmgno1$21n8$1@news.hub.org> (raw)
References: <Pine.LNX.4.58.0511282217470.13586@josh.db>
<438BD013.1000804@boreham.org>
"David Boreham" <david_list@boreham.org> wrote
>
> BTW, I heard a long time ago that NTFS has quite fancy read-ahead, where
> it attempts to detect the application's access pattern including if it is
> reading sequentially and even if there is a 'stride' to the accesses when
> they're not contiguous. I would imagine that other filesystems attempt
> similar tricks. So one might expect a simple linear prefectch
> to not help much in the presence of such a filesystem.
>
So we need more tests. I understand how smart current file systems are, and
seems that depends on the interval that you send next file block read
request (decided by cpu_cost parameter in my program).
I imagine on a multi-way machine with strong IO device, the ice-breaker
could do much better ...
> Were you worried about the icebreaker thread getting too far ahead of the
> scan ? If it did it might page out the data you're about to read, I think.
> Of course this could be fixed by having the read ahead thread perodically
> check the current location being read by the query thread and pausing if
> it's got too far ahead.
>
Right.
Regards,
Qingqing
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: zhouqq@cs.toronto.edu
Subject: Re: ice-broker scan thread
In-Reply-To: <dmgno1$21n8$1@news.hub.org>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox