linux-kernel - Re: [RFC v3 09/13] vfs: add one wq to update map info periodically

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Message-ID: <20121018022530.GB24939@gmail.com>
Date:	Thu, 18 Oct 2012 10:25:30 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	Zhi Yong Wu <zwu.kernel@...il.com>
Cc:	Dave Chinner <david@...morbit.com>, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxram@...ux.vnet.ibm.com,
	viro@...iv.linux.org.uk, dave@...os.cz, tytso@....edu,
	cmm@...ibm.com, Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
Subject: Re: [RFC v3 09/13] vfs: add one wq to update map info periodically

On Wed, Oct 17, 2012 at 02:34:15PM +0800, Zhi Yong Wu wrote:
> >> diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
> >> index d19e64a..7a79a6d 100644
> >> --- a/fs/hot_tracking.h
> >> +++ b/fs/hot_tracking.h
> >> @@ -36,6 +36,9 @@
> >>   */
> >>  #define TIME_TO_KICK 400
> >>
> >> +/* set how often to update temperatures (seconds) */
> >> +#define HEAT_UPDATE_DELAY 400
> >
> > FWIW, 400 seconds is an unusual time period. It's expected that
> > periodic work might take place at intervals of 5 minutes, 10
> > minutes, etc, not 6m40s. It's much easier to predict and understand
> > behaviour if it's at a interval of whole units like minutes,
> > especially when looking at timestamped event traces. Hence 300s (5
> > minutes) makes a lot more sense as a period for updates...
> got it. thanks.

Hi Zhi Yong,

IMHO we'd better to make this value parameterized, and then the user
can adjust this value dynamically.

Regards,
Zheng
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