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
