[PATCH net-next v6 01/10] xsk: align &xdp_buff_xsk harder

[Alexander Lobakin <aleksander.lobakin@intel.com>]

After the series "XSk buff on a diet" by Maciej, the greatest pow-2
which &xdp_buff_xsk can be divided got reduced from 16 to 8 on x86_64.
Also, sizeof(xdp_buff_xsk) now is 120 bytes, which, taking the previous
sentence into account, leads to that it leaves 8 bytes at the end of
cacheline, which means an array of buffs will have its elements
messed between the cachelines chaotically.
Use __aligned_largest for this struct. This alignment is usually 16
bytes, which makes it fill two full cachelines and align an array
nicely. ___cacheline_aligned may be excessive here, especially on
arches with 128-256 byte CLs, as well as 32-bit arches (76 -> 96
bytes on MIPS32R2), while not doing better than _largest.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 include/net/xsk_buff_pool.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index bb03cee716b3..7637799b6c19 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -29,7 +29,7 @@ struct xdp_buff_xsk {
 	dma_addr_t frame_dma;
 	struct xsk_buff_pool *pool;
 	struct list_head list_node;
-};
+} __aligned_largest;
 
 #define XSK_CHECK_PRIV_TYPE(t) BUILD_BUG_ON(sizeof(t) > offsetofend(struct xdp_buff_xsk, cb))
 #define XSK_TX_COMPL_FITS(t) BUILD_BUG_ON(sizeof(struct xsk_tx_metadata_compl) > sizeof(t))
-- 
2.47.0