On Tue, Apr 20, 2010 at 03:51:22PM -0700, Andrew Morton wrote: > On Mon, 19 Apr 2010 20:27:43 -0300 > Marcelo Jimenez <mroberto@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > I get this warning while compiling for ARM/SA1100: > > > > mm/sparse.c: In function '__section_nr': > > mm/sparse.c:135: warning: 'root' is used uninitialized in this function > > > > With a small patch in fs/proc/meminfo.c, I find that NR_SECTION_ROOTS > > is zero, which certainly explains the warning. > > > > # cat /proc/meminfo > > NR_SECTION_ROOTS=0 > > NR_MEM_SECTIONS=32 > > SECTIONS_PER_ROOT=512 > > SECTIONS_SHIFT=5 > > MAX_PHYSMEM_BITS=32 > > hm, who owns sparsemem nowadays? Nobody identifiable. > The closest entity to a SPARSEMEM owner was Andy Whitcroft but I don't believe he is active in mainline at the moment. I used to know SPARSEMEM to some extent but my memory is limited at the best of times. > Does it make physical sense to have SECTIONS_PER_ROOT > NR_MEM_SECTIONS? > Yes. NR_MEM_SECTIONS depends on MAX_PHYSMEM_BITS but SECTIONS_PER_ROOT is based on PAGE_SIZE. If MAX_PHYSMEM_BITS is particularly small due to architectural limitations, it's perfectly possible there are fewer sections that can be active (NR_MEM_SECTIONS) than is possible to fit within one root. While not physicaly impossible, it was probably not expected. Using DIV_ROUND_UP on SECTIONS_PER_ROOT to ensure NR_MEM_SECTIONS is aligned to SECTIONS_PER_ROOT should be a fix for this. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>