On Tue, Dec 1, 2009 at 6:58 PM, Benjamin Herrenschmidt <b...@kernel.crashing.org> 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 with other OS'es to have the same cache >> property to avoid cache paradoxes. Second, enabling application to map >> memory which is not managed by kernel as cacheable for better performance. > > But that doesn't solve the problem of those same pages being mapped > cachable as part of the linear mapping does it ?
I think that it doesn't has this problem. Only regions out of lmb.memory are configurable through device tree. > > Can you tell us more about your precise usage scenario ? What are you 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. 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 application/device. We need being able to map the region cachable for better performance. > trying to achieve here ? We can find a solution though it might involve > a specific driver to handle that memory. Right, but what the user to kernel API should be used? Is it ok to use the O_SYNC flag as I previously proposed? - Leo _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
