On Fri, Nov 20, 2009 at 5:03 PM, Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote: > On Fri, 2009-11-20 at 11:00 +0800, Li Yang-R58472 wrote: >> Because there is no way to set mapped memory as cacheable if the >> memory >> is not managed by Linux kernel. While, it's not rare in real system >> to >> allocate some dedicated memory to a certain application which is not >> managed by kernel and then mmap'ed the memory to the application. The >> memory should be cacheable but we can't map it to be cacheable due to >> this intelligent setting. And it is a big hit to the performance. >> Moreover, the standard O_SYNC flag suggest that user has the control >> over cacheablity, but actually we had not. > > You need to be a bit more careful tho. You must not allow RAM managed by > the kernel to be mapped non-cachable.
Even if the user explicitly sets the O_SYNC flag? IMHO, it's a bug of the application if it uses O_SYNC on main memory to be mmap'ed later. And we don't need to cover up the bug. - Leo _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev