| Message ID | 1445238646-9379-1-git-send-email-yalin.wang2010@gmail.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
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? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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;
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(-)