On Tue 25-07-17 18:31:10, Kirill A. Shutemov wrote: > On Tue, Jul 25, 2017 at 05:23:00PM +0200, Michal Hocko wrote: > > what is stdev? > > Updated tables: > > 3 runs before the patch: > Min. 1st Qu. Median Mean 3rd Qu. Max. Stdev > 177200 205000 212900 217800 223700 2377000 32868 > 172400 201700 209700 214300 220600 1343000 31191 > 175700 203800 212300 217100 223000 1061000 31195 > > 3 runs after the patch: > Min. 1st Qu. Median Mean 3rd Qu. Max. Stdev > 175900 204800 213000 216400 223600 1989000 27210 > 180300 210900 219600 223600 230200 3184000 32609 > 182100 212500 222000 226200 232700 1473000 32138 High std/avg ~15% matches my measurements (mine were even higher ~20%) and that would suggest that 3% average difference is still somehing within a "noise". Anyway, I do not really need to take the lock unless the task is the oom victim. Could you try whether those numbers improve if the lock is conditional? Thanks! --- diff --git a/mm/mmap.c b/mm/mmap.c index 0eeb658caa30..ca8a274485f8 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -44,6 +44,7 @@ #include <linux/userfaultfd_k.h> #include <linux/moduleparam.h> #include <linux/pkeys.h> +#include <linux/oom.h> #include <linux/uaccess.h> #include <asm/cacheflush.h> @@ -2997,7 +2998,8 @@ void exit_mmap(struct mm_struct *mm) * oom reaper might race with exit_mmap so make sure we won't free * page tables or unmap VMAs under its feet */ - down_write(&mm->mmap_sem); + if (tsk_is_oom_victim(current)) + down_write(&mm->mmap_sem); free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING); tlb_finish_mmu(&tlb, 0, -1); @@ -3012,7 +3014,8 @@ void exit_mmap(struct mm_struct *mm) } mm->mmap = NULL; vm_unacct_memory(nr_accounted); - up_write(&mm->mmap_sem); + if (tsk_is_oom_victim(current)) + up_write(&mm->mmap_sem); } /* Insert vm structure into process list sorted by address -- Michal Hocko SUSE Labs -- 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>
