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authorRobin Holt <holt@sgi.com>2005-11-13 16:06:42 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-13 18:14:12 -0800
commit51c6f666fceb3184eeff045dad4432b602cd648e (patch)
tree33e29916e0fea872ba6f29eba698219a740b078f /include
parent885036d32f5d3c427c3e2b385b5a5503805e3e52 (diff)
downloadop-kernel-dev-51c6f666fceb3184eeff045dad4432b602cd648e.zip
op-kernel-dev-51c6f666fceb3184eeff045dad4432b602cd648e.tar.gz
[PATCH] mm: ZAP_BLOCK causes redundant work
The address based work estimate for unmapping (for lockbreak) is and always was horribly inefficient for sparse mappings. The problem is most simply explained with an example: If we find a pgd is clear, we still have to call into unmap_page_range PGDIR_SIZE / ZAP_BLOCK_SIZE times, each time checking the clear pgd, in order to progress the working address to the next pgd. The fundamental way to solve the problem is to keep track of the end address we've processed and pass it back to the higher layers. From: Nick Piggin <npiggin@suse.de> Modification to completely get away from address based work estimate and instead use an abstract count, with a very small cost for empty entries as opposed to present pages. On 2.6.14-git2, ppc64, and CONFIG_PREEMPT=y, mapping and unmapping 1TB of virtual address space takes 1.69s; with the following patch applied, this operation can be done 1000 times in less than 0.01s From: Andrew Morton <akpm@osdl.org> With CONFIG_HUTETLB_PAGE=n: mm/memory.c: In function `unmap_vmas': mm/memory.c:779: warning: division by zero Due to zap_work -= (end - start) / (HPAGE_SIZE / PAGE_SIZE); So make the dummy HPAGE_SIZE non-zero Signed-off-by: Robin Holt <holt@sgi.com> Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/hugetlb.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 0cea162..1056717 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -102,8 +102,8 @@ static inline unsigned long hugetlb_total_pages(void)
#define hugetlb_fault(mm, vma, addr, write) ({ BUG(); 0; })
#ifndef HPAGE_MASK
-#define HPAGE_MASK 0 /* Keep the compiler happy */
-#define HPAGE_SIZE 0
+#define HPAGE_MASK PAGE_MASK /* Keep the compiler happy */
+#define HPAGE_SIZE PAGE_SIZE
#endif
#endif /* !CONFIG_HUGETLB_PAGE */
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