A long time ago, we decided to limit the number of VMAs per process to 64k. As it turns out, there actually are programs using tens of thousands of VMAs. The linear search in arch_get_unmapped_area and arch_get_unmapped_area_topdown can be a real issue for those programs. This patch series aims to fix the scalability issue by tracking the size of each free hole in the VMA rbtree, propagating the free hole info up the tree. Another major goal is to put the bulk of the necessary arch_get_unmapped_area(_topdown) functionality into one set of functions, so we can eliminate the custom large functions per architecture, sticking to a few much smaller architecture specific functions instead. In this version I have only gotten rid of the x86, ARM and MIPS arch-specific code, and am already showing a fairly promising diffstat: arch/arm/include/asm/pgtable.h | 6 arch/arm/mm/init.c | 3 arch/arm/mm/mmap.c | 217 ------------------ arch/mips/include/asm/page.h | 2 arch/mips/include/asm/pgtable.h | 7 arch/mips/mm/mmap.c | 177 -------------- arch/x86/include/asm/elf.h | 3 arch/x86/include/asm/pgtable_64.h | 4 arch/x86/kernel/sys_x86_64.c | 200 ++-------------- arch/x86/vdso/vma.c | 2 include/linux/mm_types.h | 8 include/linux/sched.h | 13 + mm/internal.h | 5 mm/mmap.c | 455 ++++++++++++++++++++++++++++++-------- 14 files changed, 420 insertions(+), 682 deletions(-) TODO: - eliminate arch-specific functions for more architectures - integrate hugetlbfs alignment (with Andi Kleen's patch?) Performance Testing performance with a benchmark that allocates tens of thousands of VMAs, unmaps them and mmaps them some more in a loop, shows promising results. Vanilla 3.4 kernel: $ ./agua_frag_test_64 .......... Min Time (ms): 6 Avg. Time (ms): 294.0000 Max Time (ms): 609 Std Dev (ms): 113.1664 Standard deviation exceeds 10 With patches: $ ./agua_frag_test_64 .......... Min Time (ms): 14 Avg. Time (ms): 38.0000 Max Time (ms): 60 Std Dev (ms): 3.9312 All checks pass The total run time of the test goes down by about a factor 4. More importantly, the worst case performance of the loop (which is what really hurt some applications) has gone down by about a factor 10. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>