Subject: Re: Adding -nomtime to the kernel
To: Darren Reed <>
From: Andrew Doran <>
List: tech-kern
Date: 09/16/2007 01:58:42
On Sat, Sep 15, 2007 at 04:28:16PM -0700, Darren Reed wrote:

> Playing around with a filesystem based database, such as postgres,
> is an interesting experience in trying to keep it running fast...some
> of the tweaks are db related, some not...
> For example, if the db is serving queries every second or so,
> then there's a lot of "atime" updates that happen and mounting the
> filesystem with -noatime has a noticable impact on performance.
> Having done that, I'm wondering if it makes sense for NetBSD
> to support -nomtime as well.  I'm not sure what impact this will
> have on postgres's operation (does it depend on file modification
> timestamp changes?) but I'm semi-willing to give it a shot.
> Does anyone else have any thoughts/criticisms/experience on this?

My understanding is that inode time updates are deferred, but I haven't
checked that. Maybe we have a bug? Updating the times but doing it
infrequently seems like the best way to handle it.