Re: [PATCH 00/23] per device dirty throttling -v8

David Chinner
2007-08-05T23:45:13Z

On Sun, Aug 05, 2007 at 06:42:30AM -0400, Jeff Garzik wrote:
> Jakob Oestergaard wrote:
> >Oh dear.
> >
> >Why not just make ext3 fsync() a no-op while you're at it?
> >
> >Distros can turn it back on if it's needed...
> >
> >Of course I'm not serious, but like atime, fsync() is something one
>
> No, they are nothing alike, and you are just making yourself look silly
> if you compare them. fsync has to do with fundamental guarantees about
> data.

Hi Jeff - just as a point to note, I think you should check the spec
for fsync before stating that:

"It is explicitly intended that a null implementation is permitted."

and

"... fsync() might or might not actually cause data to be written where it is
safe from a power failure."

http://www.opengroup.org/onlinepubs/009695399/functions/fsync.html

So fsync() does not have to provide the fundamental guarantees you think
it should.

Note - I'm not saying that this is at all sane (it's crazy, IMO), I'm just
pointing out that a "nofsync" mount option to avoid fsync overhead is a
legal thing to do....

Cheers,

Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group