Searched hist:"5 f70b962" (Results 1 – 1 of 1) sorted by relevance
/openbmc/linux/mm/ |
H A D | mmap.c | 5f70b962 Tue May 24 19:11:19 CDT 2011 Shaohua Li <shaohua.li@intel.com> mmap: avoid unnecessary anon_vma lock
If we only change vma->vm_end, we can avoid taking anon_vma lock even if 'insert' isn't NULL, which is the case of split_vma.
As I understand it, we need the lock before because rmap must get the 'insert' VMA when we adjust old VMA's vm_end (the 'insert' VMA is linked to anon_vma list in __insert_vm_struct before).
But now this isn't true any more. The 'insert' VMA is already linked to anon_vma list in __split_vma(with anon_vma_clone()) instead of __insert_vm_struct. There is no race rmap can't get required VMAs. So the anon_vma lock is unnecessary, and this can reduce one locking in brk case and improve scalability.
Signed-off-by: Shaohua Li<shaohua.li@intel.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 5f70b962 Tue May 24 19:11:19 CDT 2011 Shaohua Li <shaohua.li@intel.com> mmap: avoid unnecessary anon_vma lock If we only change vma->vm_end, we can avoid taking anon_vma lock even if 'insert' isn't NULL, which is the case of split_vma. As I understand it, we need the lock before because rmap must get the 'insert' VMA when we adjust old VMA's vm_end (the 'insert' VMA is linked to anon_vma list in __insert_vm_struct before). But now this isn't true any more. The 'insert' VMA is already linked to anon_vma list in __split_vma(with anon_vma_clone()) instead of __insert_vm_struct. There is no race rmap can't get required VMAs. So the anon_vma lock is unnecessary, and this can reduce one locking in brk case and improve scalability. Signed-off-by: Shaohua Li<shaohua.li@intel.com> Cc: Rik van Riel <riel@redhat.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|