2017-07-16 07:28:35

by Zhaoyang Huang

Subject: [PATCH] mm/vmalloc: terminate searching since one node found

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

Signed-off-by: Zhaoyang Huang <[email protected]>
Signed-off-by: Zhaoyang Huang <[email protected]>
---
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

2017-07-17 07:00:31

by Michal Hocko

Subject: Re: [PATCH] mm/vmalloc: terminate searching since one node found

On Sun 16-07-17 15:28:27, Zhaoyang Huang wrote:
> 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

Please describe _why_ the patch is needed. I suspect this is an
optimization but for which workloads it matters and how much.

> Signed-off-by: Zhaoyang Huang <[email protected]>
> Signed-off-by: Zhaoyang Huang <[email protected]>

no need to to make your s-o-b twice. Just use the same one as the From
(author of the patch).

> ---
> 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
>

--
Michal Hocko
SUSE Labs