On Mon, Mar 03, 2014 at 02:06:18PM +0000, Markos Chandras wrote: > On 02/21/2014 05:38 PM, Ralf Baechle wrote: > >On Thu, Feb 20, 2014 at 02:00:26PM +0000, Markos Chandras wrote: > > > >>From: Paul Burton <paul.burton@xxxxxxxxxx> > >> > >>For Malta defconfigs which may run on an SMP configuration without > >>hardware cache anti-aliasing, a 16KB page size is a safer default. > >>Most notably at the moment it will avoid cache aliasing issues for > >>multicore proAptiv systems. > > > >You're aware that this may cause binary compatibility issues with old > >userland? So far the defaults were chosen to maximise compatibility > >over performance. > > > > Ralf > > > Hi Ralf, > > Are you referring to programs hard coding the page size to 4k instead of > using the getpagesize()? Well yes this could be a problem. But is that a > real problem? We are changing the default value so whoever has such an old > userland can easily switch to the 4k page size. It may also be a good > opportunity to expose such application and get the fixed properly :) But if > that's not acceptable, we can drop the patch. Paul what do you think? > > -- > markos I think the potential backwards compatibility issue is probably not a huge issue for Malta, but that it would make sense to dig deeper into why proAptiv SMP systems don't run correctly with 4KB pages. You don't actually have to look very far to find userland which depends upon 4KB pages (*cough* android *cough*). I consider this patch an acceptable workaround for the proAptiv problem on Malta, but I don't know enough at the moment to say whether there's a proper fix. Paul
