* [RFC] bpf: change bpf syacall to use u64 temp variables
@ 2015-10-19 7:10 yalin wang
2015-10-19 8:55 ` Daniel Borkmann
2015-10-19 19:08 ` Alexei Starovoitov
0 siblings, 2 replies; 3+ messages in thread
From: yalin wang @ 2015-10-19 7:10 UTC (permalink / raw)
To: ast, netdev, linux-kernel; +Cc: yalin wang
This patch change map_lookup_elem() and map_update_elem() function
to use u64 temp variable if the key_size or value_size is less than
u64, we don't need use kmalloc() for these small variables.
Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
---
kernel/bpf/syscall.c | 30 ++++++++++++++++++++----------
1 file changed, 20 insertions(+), 10 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index f640e5f..c82d7bf 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -189,7 +189,8 @@ static int map_lookup_elem(union bpf_attr *attr)
void __user *uvalue = u64_to_ptr(attr->value);
int ufd = attr->map_fd;
struct bpf_map *map;
- void *key, *value, *ptr;
+ u64 key_buf, value_buf;
+ void *key = &key_buf, *value = &value_buf, *ptr;
struct fd f;
int err;
@@ -202,7 +203,8 @@ static int map_lookup_elem(union bpf_attr *attr)
return PTR_ERR(map);
err = -ENOMEM;
- key = kmalloc(map->key_size, GFP_USER);
+ if (map->key_size > sizeof(u64))
+ key = kmalloc(map->key_size, GFP_USER);
if (!key)
goto err_put;
@@ -211,7 +213,8 @@ static int map_lookup_elem(union bpf_attr *attr)
goto free_key;
err = -ENOMEM;
- value = kmalloc(map->value_size, GFP_USER);
+ if (map->value_size > sizeof(u64))
+ value = kmalloc(map->value_size, GFP_USER);
if (!value)
goto free_key;
@@ -232,9 +235,11 @@ static int map_lookup_elem(union bpf_attr *attr)
err = 0;
free_value:
- kfree(value);
+ if (value != &value_buf)
+ kfree(value);
free_key:
- kfree(key);
+ if (key != &key_buf)
+ kfree(key);
err_put:
fdput(f);
return err;
@@ -248,7 +253,8 @@ static int map_update_elem(union bpf_attr *attr)
void __user *uvalue = u64_to_ptr(attr->value);
int ufd = attr->map_fd;
struct bpf_map *map;
- void *key, *value;
+ u64 key_buf, value_buf;
+ void *key = &key_buf, *value = &value_buf;
struct fd f;
int err;
@@ -261,7 +267,8 @@ static int map_update_elem(union bpf_attr *attr)
return PTR_ERR(map);
err = -ENOMEM;
- key = kmalloc(map->key_size, GFP_USER);
+ if (map->key_size > sizeof(u64))
+ key = kmalloc(map->key_size, GFP_USER);
if (!key)
goto err_put;
@@ -270,7 +277,8 @@ static int map_update_elem(union bpf_attr *attr)
goto free_key;
err = -ENOMEM;
- value = kmalloc(map->value_size, GFP_USER);
+ if (map->value_size > sizeof(u64))
+ value = kmalloc(map->value_size, GFP_USER);
if (!value)
goto free_key;
@@ -286,9 +294,11 @@ static int map_update_elem(union bpf_attr *attr)
rcu_read_unlock();
free_value:
- kfree(value);
+ if (value != &value_buf)
+ kfree(value);
free_key:
- kfree(key);
+ if (key != &key_buf)
+ kfree(key);
err_put:
fdput(f);
return err;
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC] bpf: change bpf syacall to use u64 temp variables
2015-10-19 7:10 [RFC] bpf: change bpf syacall to use u64 temp variables yalin wang
@ 2015-10-19 8:55 ` Daniel Borkmann
2015-10-19 19:08 ` Alexei Starovoitov
1 sibling, 0 replies; 3+ messages in thread
From: Daniel Borkmann @ 2015-10-19 8:55 UTC (permalink / raw)
To: yalin wang, ast, netdev, linux-kernel
On 10/19/2015 09:10 AM, yalin wang wrote:
> This patch change map_lookup_elem() and map_update_elem() function
> to use u64 temp variable if the key_size or value_size is less than
> u64, we don't need use kmalloc() for these small variables.
>
> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
From an application PoV that has to make the bpf(2) syscall, how
much do we actually gain from this? I'm curious, did you perform
some benchmarks that show a noticeable difference?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [RFC] bpf: change bpf syacall to use u64 temp variables
2015-10-19 7:10 [RFC] bpf: change bpf syacall to use u64 temp variables yalin wang
2015-10-19 8:55 ` Daniel Borkmann
@ 2015-10-19 19:08 ` Alexei Starovoitov
1 sibling, 0 replies; 3+ messages in thread
From: Alexei Starovoitov @ 2015-10-19 19:08 UTC (permalink / raw)
To: yalin wang; +Cc: ast, netdev, linux-kernel
On Mon, Oct 19, 2015 at 03:10:46PM +0800, yalin wang wrote:
> This patch change map_lookup_elem() and map_update_elem() function
> to use u64 temp variable if the key_size or value_size is less than
> u64, we don't need use kmalloc() for these small variables.
>
> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
> ---
> kernel/bpf/syscall.c | 30 ++++++++++++++++++++----------
> 1 file changed, 20 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index f640e5f..c82d7bf 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -189,7 +189,8 @@ static int map_lookup_elem(union bpf_attr *attr)
> void __user *uvalue = u64_to_ptr(attr->value);
> int ufd = attr->map_fd;
> struct bpf_map *map;
> - void *key, *value, *ptr;
> + u64 key_buf, value_buf;
> + void *key = &key_buf, *value = &value_buf, *ptr;
> struct fd f;
> int err;
>
> @@ -202,7 +203,8 @@ static int map_lookup_elem(union bpf_attr *attr)
> return PTR_ERR(map);
>
> err = -ENOMEM;
> - key = kmalloc(map->key_size, GFP_USER);
> + if (map->key_size > sizeof(u64))
> + key = kmalloc(map->key_size, GFP_USER);
I think it's a good optimization for common case.
Performance numbers would be good to prove the point.
Thanks
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-10-19 7:10 [RFC] bpf: change bpf syacall to use u64 temp variables yalin wang
2015-10-19 8:55 ` Daniel Borkmann
2015-10-19 19:08 ` Alexei Starovoitov
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