Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-03 Thread Benjamin Herrenschmidt
On Tue, 2009-12-01 at 15:35 +0100, Segher Boessenkool wrote: > So make the memory known to the kernel, just tell the kernel not to > use it. If it's normal system RAM, just put it in the "memory" node > and do a memreserve on it (or do something in your platform code); if > it's some other memory,

Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-03 Thread Benjamin Herrenschmidt
On Tue, 2009-12-01 at 19:34 +0800, Li Yang wrote: > The scenario for the second case is to pre-allocate some memory to a > certain application or device (probably through mem=XXX kernel > parameter or limit through device tree). The memory is not known to > kernel, but fully managed by the applica

Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-02 Thread Li Yang
On Thu, Dec 3, 2009 at 12:15 PM, Segher Boessenkool wrote: The scenario for the first case is that in a multicore system running ASMP which means different OS runs on different cores.  They might communicate through a shared memory region.  The region on every OS need to be map

Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-02 Thread Segher Boessenkool
The scenario for the first case is that in a multicore system running ASMP which means different OS runs on different cores. They might communicate through a shared memory region. The region on every OS need to be mapped with the same cache perperty to avoid cache paradox. This isn't true.

Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-01 Thread Li Yang
On Tue, Dec 1, 2009 at 10:35 PM, Segher Boessenkool wrote: >> The scenario for the first case is that in a multicore system running >> ASMP which means different OS runs on different cores.  They might >> communicate through a shared memory region.  The region on every OS >> need to be mapped with

Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-01 Thread Segher Boessenkool
The scenario for the first case is that in a multicore system running ASMP which means different OS runs on different cores. They might communicate through a shared memory region. The region on every OS need to be mapped with the same cache perperty to avoid cache paradox. This isn't true. In

Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-01 Thread Li Yang
On Tue, Dec 1, 2009 at 6:58 PM, Benjamin Herrenschmidt wrote: > On Tue, 2009-12-01 at 18:30 +0800, Li Yang wrote: >> The patch adds the ability for powerpc architecture to set page cache >> property of mmaped area through device tree.  This is useful for two >> cases.  First, for memory shared wit

Re: [PATCH] powerpc/mm: setting mmaped page cache property through device tree

2009-12-01 Thread Benjamin Herrenschmidt
On Tue, 2009-12-01 at 18:30 +0800, Li Yang wrote: > The patch adds the ability for powerpc architecture to set page cache > property of mmaped area through device tree. This is useful for two > cases. First, for memory shared with other OS'es to have the same cache > property to avoid cache parad