On Fri, 3 Feb 2012, Lars Heidieker wrote: > On Fri, Feb 3, 2012 at 6:49 PM, Eduardo Horvath <e...@netbsd.org> wrote: > > On Fri, 3 Feb 2012, Lars Heidieker wrote: > > > >> The code for proper kmem_arena sizing: > >> http://www.netbsd.org/~para/kmemsizing.diff > >> > >> params done for i386/amd64/sparc64/arm32 > > > > Explain this to me: > > > > /* > > - * Minimum and maximum sizes of the kernel malloc arena in > > PAGE_SIZE-sized > > + * Minimum size of the kernel kmem_arena in PAGE_SIZE-sized > > * logical pages. > > + * No enforced maximum on sparc64. > > */ > > -#define NKMEMPAGES_MIN_DEFAULT ((6 * 1024 * 1024) >> PAGE_SHIFT) > > -#define NKMEMPAGES_MAX_DEFAULT ((128 * 1024 * 1024) >> > > PAGE_SHIFT) > > +#define NKMEMPAGES_MIN_DEFAULT ((64 * 1024 * 1024) >> PAGE_SHIFT) > > +#define NKMEMPAGES_MAX_UNLIMITED 1 > > > > > > Does this mean a machine needs to allocate a minimum of 64MB for the > > kernel kmem_arena or it won't boot? What happens if a machine only has > > 64MB of DRAM? > > > > It's not about physcial memory, it's sizing the kmem_arenas virtual size. > It is sized by physical memory size as an aproximation, with a certain > lower limit and if required an upper bound. > The upper bound is only required on archs that have limited kernel > virtual memory space (in comparison to physical memory) eg i386 as 1GB > virtual memory kernel space but probably 2-3GB physcial memory. So the > kmem_arena is the limited to 280MB to leave space for other maps uares > buffers.
Interesting, but it didn't really answer the question. Will it attempt to allocate NKMEMPAGES_MIN_DEFAULT pages on startup? Will this break machines with 64MB of RAM? 'Cause I don't think that's something we want to do. Eduardo
