On Mon 17-07-17 15:27:31, Zhaoyang Huang wrote:
> From: Zhaoyang Huang <zhaoyang.hu...@spreadtrum.com:wq>
> 
> It is no need to find the very beginning of the area within
> alloc_vmap_area, which can be done by judging each node during the process
> 
> For current approach, the worst case is that the starting node which be found
> for searching the 'vmap_area_list' is close to the 'vstart', while the final
> available one is round to the tail(especially for the left branch).
> This commit have the list searching start at the first available node, which
> will save the time of walking the rb tree'(1)' and walking the list(2).
> 
>       vmap_area_root
>           /      \
>      tmp_next     U
>         /   (1)
>       tmp
>        /
>      ...
>       /
>     first(current approach)
> 
> vmap_area_list->...->first->...->tmp->tmp_next
>                             (2)

This still doesn't answer questions posted for your previous version
http://lkml.kernel.org/r/20170717070024.gc7...@dhcp22.suse.cz

Please note that is really important to describe _why_ the patch is
needed. What has changed can be easily read in the diff...

> Signed-off-by: Zhaoyang Huang <zhaoyang.hu...@spreadtrum.com>
> ---
>  mm/vmalloc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 34a1c3e..f833e07 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -459,9 +459,16 @@ static struct vmap_area *alloc_vmap_area(unsigned long 
> size,
>  
>               while (n) {
>                       struct vmap_area *tmp;
> +                     struct vmap_area *tmp_next;
>                       tmp = rb_entry(n, struct vmap_area, rb_node);
> +                     tmp_next = list_next_entry(tmp, list);
>                       if (tmp->va_end >= addr) {
>                               first = tmp;
> +                             if (ALIGN(tmp->va_end, align) + size
> +                                             < tmp_next->va_start) {
> +                                     addr = ALIGN(tmp->va_end, align);
> +                                     goto found;
> +                             }
>                               if (tmp->va_start <= addr)
>                                       break;
>                               n = n->rb_left;
> -- 
> 1.9.1
> 
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-- 
Michal Hocko
SUSE Labs

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