Re: [PATCHv6 net-next 1/3] net: erspan: use bitfield instead of mask and offset

[Pravin Shelar]

On Thu, Jan 25, 2018 at 1:20 PM, William Tu  wrote:
> Originally the erspan fields are defined as a group into a __be16 field,
> and use mask and offset to access each field.  This is more costly due to
> calling ntohs/htons.  The patch changes it to use bitfields.
>
> Signed-off-by: William Tu 

Acked-by: Pravin B Shelar 

Thanks.

[PATCHv6 net-next 1/3] net: erspan: use bitfield instead of mask and offset

[William Tu]

Originally the erspan fields are defined as a group into a __be16 field,
and use mask and offset to access each field.  This is more costly due to
calling ntohs/htons.  The patch changes it to use bitfields.

Signed-off-by: William Tu 
---
 include/net/erspan.h | 127 ++-
 net/ipv4/ip_gre.c|  38 ++-
 net/ipv6/ip6_gre.c   |  36 ++-
 3 files changed, 121 insertions(+), 80 deletions(-)

diff --git a/include/net/erspan.h b/include/net/erspan.h
index 712ea1b1f4db..6d30fe898286 100644
--- a/include/net/erspan.h
+++ b/include/net/erspan.h
@@ -65,16 +65,30 @@
 #define GRA_MASK   0x0006
 #define O_MASK 0x0001
 
+#define HWID_OFFSET4
+#define DIR_OFFSET 3
+
 /* ERSPAN version 2 metadata header */
 struct erspan_md2 {
__be32 timestamp;
__be16 sgt; /* security group tag */
-   __be16 flags;
-#define P_OFFSET   15
-#define FT_OFFSET  10
-#define HWID_OFFSET4
-#define DIR_OFFSET 3
-#define GRA_OFFSET 1
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+   __u8hwid_upper:2,
+   ft:5,
+   p:1;
+   __u8o:1,
+   gra:2,
+   dir:1,
+   hwid:4;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+   __u8p:1,
+   ft:5,
+   hwid_upper:2;
+   __u8hwid:4,
+   dir:1,
+   gra:2,
+   o:1;
+#endif
 };
 
 enum erspan_encap_type {
@@ -95,15 +109,62 @@ struct erspan_metadata {
 };
 
 struct erspan_base_hdr {
-   __be16 ver_vlan;
-#define VER_OFFSET  12
-   __be16 session_id;
-#define COS_OFFSET  13
-#define EN_OFFSET   11
-#define BSO_OFFSET  EN_OFFSET
-#define T_OFFSET10
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+   __u8vlan_upper:4,
+   ver:4;
+   __u8vlan:8;
+   __u8session_id_upper:2,
+   t:1,
+   en:2,
+   cos:3;
+   __u8session_id:8;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+   __u8ver: 4,
+   vlan_upper:4;
+   __u8vlan:8;
+   __u8cos:3,
+   en:2,
+   t:1,
+   session_id_upper:2;
+   __u8session_id:8;
+#else
+#error "Please fix "
+#endif
 };
 
+static inline void set_session_id(struct erspan_base_hdr *ershdr, u16 id)
+{
+   ershdr->session_id = id & 0xff;
+   ershdr->session_id_upper = (id >> 8) & 0x3;
+}
+
+static inline u16 get_session_id(const struct erspan_base_hdr *ershdr)
+{
+   return (ershdr->session_id_upper << 8) + ershdr->session_id;
+}
+
+static inline void set_vlan(struct erspan_base_hdr *ershdr, u16 vlan)
+{
+   ershdr->vlan = vlan & 0xff;
+   ershdr->vlan_upper = (vlan >> 8) & 0xf;
+}
+
+static inline u16 get_vlan(const struct erspan_base_hdr *ershdr)
+{
+   return (ershdr->vlan_upper << 8) + ershdr->vlan;
+}
+
+static inline void set_hwid(struct erspan_md2 *md2, u8 hwid)
+{
+   md2->hwid = hwid & 0xf;
+   md2->hwid_upper = (hwid >> 4) & 0x3;
+}
+
+static inline u8 get_hwid(const struct erspan_md2 *md2)
+{
+   return (md2->hwid_upper << 4) + md2->hwid;
+}
+
 static inline int erspan_hdr_len(int version)
 {
return sizeof(struct erspan_base_hdr) +
@@ -120,7 +181,7 @@ static inline u8 tos_to_cos(u8 tos)
 }
 
 static inline void erspan_build_header(struct sk_buff *skb,
-   __be32 id, u32 index,
+   u32 id, u32 index,
bool truncate, bool is_ipv4)
 {
struct ethhdr *eth = (struct ethhdr *)skb->data;
@@ -154,12 +215,12 @@ static inline void erspan_build_header(struct sk_buff 
*skb,
memset(ershdr, 0, sizeof(*ershdr) + ERSPAN_V1_MDSIZE);
 
/* Build base header */
-   ershdr->ver_vlan = htons((vlan_tci & VLAN_MASK) |
-(ERSPAN_VERSION << VER_OFFSET));
-   ershdr->session_id = htons((u16)(ntohl(id) & ID_MASK) |
-  ((tos_to_cos(tos) << COS_OFFSET) & COS_MASK) |
-  (enc_type << EN_OFFSET & EN_MASK) |
-  ((truncate << T_OFFSET) & T_MASK));
+   ershdr->ver = ERSPAN_VERSION;
+   ershdr->cos = tos_to_cos(tos);
+   ershdr->en = enc_type;
+   ershdr->t = truncate;
+   set_vlan(ershdr, vlan_tci);
+   set_session_id(ershdr, id);
 
/* Build metadata */
ersmd = (struct erspan_metadata *)(ershdr + 1);
@@ -187,7 +248,7 @@ static inline __be32 erspan_get_timestamp(void)
 }
 
 static inline void erspan_build_header_v2(struct sk_buff *skb,
- __be32 id, u8 direction, u16 hwid,
+ u32 id, u8 direction, u16 hwid,
  bool truncate, bool is_ipv4)
 {
struct ethhdr *eth = (struct ethhdr *)skb->data;
@@ -198,7 +259,6 @@ static inline void erspan_build_header_v2(struct sk_buff 
*skb,