Re: vfs: Add MS_FLUSHONFSYNC mount flag

["Fernando Luis Vázquez Cao" <fernando@oss.ntt.co.jp>]

On Sun, 2009-02-15 at 17:54 -0500, Theodore Tso wrote:
> On Sun, Feb 15, 2009 at 04:23:26PM +0900, Fernando Luis Vázquez Cao wrote:
> > You mentioned "we should integrate this with the barrier settings". Do
> > you imply we should make it a per-device tunable too? Should we keep the
> > barrier-related mount options some filesystems provide?
> > 
> 
> Making barriers to be a per-device tunable makes sense.  The only
> reason why we kept it as a mount option in ext4 is for benchmarking
> purposes, and in ext3, because the filesystem predated the barrier
> code, and there was a desire to be able to benchmark with and without
> the old behavior --- and because akpm is still worried about the
> performance hit of the barrier code, so he's been resistant about
> change the default for ext3.

Ok, I'll turn both barriers and flushonfsync into a sysfs-exported
per-device knob and see how it turns out.

By the way, should we also add/keep a mount option for "benchmarking
purposes"?. I guess that once we get the per-device tunable we probable
do not need it anymore.

Regards,

Fernando