[RFC net-next 1/6] xdp: reduce size of struct xdp_mem_info

Matteo Croce
2021-03-11T19:44:52Z

From: Jesper Dangaard Brouer <brouer@redhat.com>

It is possible to compress/reduce the size of struct xdp_mem_info.
This change reduce struct xdp_mem_info from 8 bytes to 4 bytes.

The member xdp_mem_info.id can be reduced to u16, as the mem_id_ht
rhashtable in net/core/xdp.c is already limited by MEM_ID_MAX=0xFFFE
which can safely fit in u16.

The member xdp_mem_info.type could be reduced more than u16, as it stores
the enum xdp_mem_type, but due to alignment it is only reduced to u16.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/xdp.h | 4 ++--
net/core/xdp.c | 8 ++++----
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index a5bc214a49d9..c35864d59113 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -48,8 +48,8 @@ enum xdp_mem_type {
#define XDP_XMIT_FLAGS_MASK XDP_XMIT_FLUSH

struct xdp_mem_info {
- u32 type; /* enum xdp_mem_type, but known size type */
- u32 id;
+ u16 type; /* enum xdp_mem_type, but known size type */
+ u16 id;
};

struct page_pool;
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 05354976c1fc..3dd47ed83778 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -35,11 +35,11 @@ static struct rhashtable *mem_id_ht;

static u32 xdp_mem_id_hashfn(const void *data, u32 len, u32 seed)
{
- const u32 *k = data;
- const u32 key = *k;
+ const u16 *k = data;
+ const u16 key = *k;

BUILD_BUG_ON(sizeof_field(struct xdp_mem_allocator, mem.id)
- != sizeof(u32));
+ != sizeof(u16));

/* Use cyclic increasing ID as direct hash key */
return key;
@@ -49,7 +49,7 @@ static int xdp_mem_id_cmp(struct rhashtable_compare_arg *arg,
const void *ptr)
{
const struct xdp_mem_allocator *xa = ptr;
- u32 mem_id = *(u32 *)arg->key;
+ u16 mem_id = *(u16 *)arg->key;

return xa->mem.id != mem_id;
}
--
2.29.2