On 08/13/2013 09:29 PM, Stanislav Kholmanskikh wrote: > > On 08/06/2013 10:52 AM, Stanislav Kholmanskikh wrote: >> On 08/05/2013 07:41 PM, [email protected] wrote: >>> Hi! >> Hi, Cyril. >>>> * kernel test for max_map_count_sysctl is: >>>> /* Too many mappings? */ >>>> if (mm->map_count > sysctl_max_map_count) >>>> return -ENOMEM; >>> Hmm, that looks like we allow the map_count to became one greater than >>> max_map_count, is this known bug? >> I'm not sure whether this is a bug or feature but in fact mm/mmap.c >> contains >> this strict condition. >> >>>> so in LTP test map_count should be greater than max_map_count by 1 >>>> >>>> * only [vsyscall] is allocated without incrementing mm->map_count >>> That also looks strange, do you know why one is allocated without >>> incrementing it and another with? >>> >> [vdso] is allocated this way: >> 1) load_elf_binary (fs/binfmt_elf.c) >> 2) arch_setup_additional_pages (arch/x86/vdso/vdso32-setup.c) >> 3) install_special_mapping (mm/mmap.c) >> 4) insert_vm_struct (mm/mmap.c) >> 5) vma_link (mm/mmap.c) increases mm->map_count++
Sorry for lately replying, as I'm a little busy these days... we all know (you have explained) VDSO vma is inserted by install_special_mapping(), and the sysctl_max_map_count don't check the special vma, that's the reason why map_count is to became one greater than max_map_count, For vsyscall vma, a kernel developer ever told me that the vma is never inserted into vma list, so sysctl_max_map_count also don't check it. I don't verify it from kernel codes, but lots of testing have proved it's right - sysctl_max_map_count didn't check the two special vma VDSO and VSYSCALL. Depending on this, I think the previous codes is right, any comments? Thanks, Zhouping ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ Ltp-list mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ltp-list
