Re: [PATCH 21/26] tty: Convert tty_struct bitfield to bools

[Greg Kroah-Hartman]

On Wed, Sep 03, 2014 at 11:10:45AM -0400, Peter Hurley wrote:
> On 09/03/2014 08:19 AM, One Thousand Gnomes wrote:
> >> Ahh. Thanks for the insight, Alan.
> >>
> >> But set_bit() et. al. will generate an incredible amount of churn;
> >> what if I split the fields up to prevent false-sharing?
> > 
> > Do you feel lucky ;-)
> 
> Hahaha  :)
> 
> > I'd rather set_bit and friends were used. They exist largely for this
> > kind of reason and they also have atomic test/set methods which may in
> > the longer term be very useful.
> > 
> > Yes it is churn can't argue with that.
> 
> Yuck. There should be a better way. IXANY mode is suddenly going to
> have a ton of unnecessary bus locks on x86.

True, but at least it will be correct, which I'm guessing today it isn't
:(

> Note the ctrl_status field is a byte as well, which can't be RMW'ed by
> the bit-locked primitives, and definitely should not be aggregated with
> any adjacent field.

Never trust what an ia64 compiler can, and will, do...

greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/