On (24/07/07 22:01), Andrew Morton didst pronounce: > On Tue, 13 Mar 2007 10:42:02 +0000 [EMAIL PROTECTED] (Mel Gorman) wrote: > > > There are problems in the use of SPARSEMEM and pageblock flags that causes > > problems on ia64. > > > > The first part of the problem is that units are incorrect in > > SECTION_BLOCKFLAGS_BITS computation. This results in a map_section's > > section_mem_map being treated as part of a bitmap which isn't good. This > > was evident with an invalid virtual address when mem_init attempted to free > > bootmem pages while relinquishing control from the bootmem allocator. > > > > The second part of the problem occurs because the pageblock flags bitmap is > > be located with the mem_section. The SECTIONS_PER_ROOT computation using > > sizeof (mem_section) may not be a power of 2 depending on the size of the > > bitmap. This renders masks and other such things not power of 2 base. This > > issue was seen with SPARSEMEM_EXTREME on ia64. This patch moves the bitmap > > outside of mem_section and uses a pointer instead in the mem_section. The > > bitmaps are allocated when the section is being initialised. > > > > Note that sparse_early_usemap_alloc() does not use alloc_remap() like > > sparse_early_mem_map_alloc(). The allocation required for the bitmap on x86, > > the only architecture that uses alloc_remap is typically smaller than a > > cache > > line. alloc_remap() pads out allocations to the cache size which would be > > a needless waste. > > > > Credit to Bob Picco for identifying the original problem and effecting a > > fix for the SECTION_BLOCKFLAGS_BITS calculation. Credit to Andy Whitcroft > > for devising the best way of allocating the bitmaps only when required for > > the section. > > SuperH allmodconfig blew up: > > mm/sparse.c: In function `sparse_init': > mm/sparse.c:482: error: implicit declaration of function > `sparse_early_usemap_alloc' > mm/sparse.c:482: warning: assignment makes pointer from integer without a cast > mm/sparse.c: In function `sparse_add_one_section': > mm/sparse.c:553: error: implicit declaration of function > `__kmalloc_section_usemap' > mm/sparse.c:553: warning: assignment makes pointer from integer without a cast
I'm looking at this now and getting a superh cross-compiler built to build-test any fix. My first impression is that sparse_early_usemap_alloc() needs to be defined whether CONFIG_SPARSEMEM_VMEMMAP is set or not. Right now, sparse_early_usemap_alloc() is only defined when it is set and it's not clear why although "by accident" is the most likely explanation. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
