[PATCH net-next 6/8] ice: reduce size of queue context fields

[Jacob Keller]

The ice_rlan_ctx and ice_tlan_ctx structures have some fields which are
intentionally sized larger necessary relative to the packed sizes the data
must fit into. This was done because the original ice_set_ctx() function
and its helpers did not correctly handle packing when the packed bits
straddled a byte. This is no longer the case with the use of the
<linux/packing.h> implementation.

Save some bytes in these structures by sizing the variables to the number
of bytes the actual bitpacked fields fit into.

There are a couple of gaps left in the structure, which is a result of the
fields being in the order they appear in the packed bit layout, but where
alignment forces some extra gaps. We could fix this, saving ~8 bytes from
each structure. However, these structures are not used heavily, and the
resulting savings is minimal:

$ bloat-o-meter ice-before-reorder.ko ice-after-reorder.ko
add/remove: 0/0 grow/shrink: 1/1 up/down: 26/-70 (-44)
Function                                     old     new   delta
ice_vsi_cfg_txq                             1873    1899     +26
ice_setup_rx_ctx.constprop                  1529    1459     -70
Total: Before=1459555, After=1459511, chg -0.00%

Thus, the fields are left in the same order as the packed bit layout,
despite the gaps this causes.

Signed-off-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx>
---
 drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h | 32 ++++++++------------------
 1 file changed, 10 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
index 6c83e9d71c64..618cc39bd397 100644
--- a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
+++ b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
@@ -377,23 +377,17 @@ enum ice_rx_flex_desc_status_error_1_bits {
 #define ICE_TX_DRBELL_Q_CTX_SIZE_DWORDS	5
 #define GLTCLAN_CQ_CNTX(i, CQ)		(GLTCLAN_CQ_CNTX0(CQ) + ((i) * 0x0800))
 
-/* RLAN Rx queue context data
- *
- * The sizes of the variables may be larger than needed due to crossing byte
- * boundaries. If we do not have the width of the variable set to the correct
- * size then we could end up shifting bits off the top of the variable when the
- * variable is at the top of a byte and crosses over into the next byte.
- */
+/* RLAN Rx queue context data */
 struct ice_rlan_ctx {
 	u16 head;
-	u16 cpuid; /* bigger than needed, see above for reason */
+	u8 cpuid;
 #define ICE_RLAN_BASE_S 7
 	u64 base;
 	u16 qlen;
 #define ICE_RLAN_CTX_DBUF_S 7
-	u16 dbuf; /* bigger than needed, see above for reason */
+	u8 dbuf;
 #define ICE_RLAN_CTX_HBUF_S 6
-	u16 hbuf; /* bigger than needed, see above for reason */
+	u8 hbuf;
 	u8 dtype;
 	u8 dsize;
 	u8 crcstrip;
@@ -401,12 +395,12 @@ struct ice_rlan_ctx {
 	u8 hsplit_0;
 	u8 hsplit_1;
 	u8 showiv;
-	u32 rxmax; /* bigger than needed, see above for reason */
+	u16 rxmax;
 	u8 tphrdesc_ena;
 	u8 tphwdesc_ena;
 	u8 tphdata_ena;
 	u8 tphhead_ena;
-	u16 lrxqthresh; /* bigger than needed, see above for reason */
+	u8 lrxqthresh;
 	u8 prefena;	/* NOTE: normally must be set to 1 at init */
 };
 
@@ -539,18 +533,12 @@ enum ice_tx_ctx_desc_eipt_offload {
 
 #define ICE_TXQ_CTX_SZ		22
 
-/* Tx queue context data
- *
- * The sizes of the variables may be larger than needed due to crossing byte
- * boundaries. If we do not have the width of the variable set to the correct
- * size then we could end up shifting bits off the top of the variable when the
- * variable is at the top of a byte and crosses over into the next byte.
- */
+/* Tx queue context data */
 struct ice_tlan_ctx {
 #define ICE_TLAN_CTX_BASE_S	7
 	u64 base;		/* base is defined in 128-byte units */
 	u8 port_num;
-	u16 cgd_num;		/* bigger than needed, see above for reason */
+	u8 cgd_num;
 	u8 pf_num;
 	u16 vmvf_num;
 	u8 vmvf_type;
@@ -561,7 +549,7 @@ struct ice_tlan_ctx {
 	u8 tsyn_ena;
 	u8 internal_usage_flag;
 	u8 alt_vlan;
-	u16 cpuid;		/* bigger than needed, see above for reason */
+	u8 cpuid;
 	u8 wb_mode;
 	u8 tphrd_desc;
 	u8 tphrd;
@@ -570,7 +558,7 @@ struct ice_tlan_ctx {
 	u16 qnum_in_func;
 	u8 itr_notification_mode;
 	u8 adjust_prof_id;
-	u32 qlen;		/* bigger than needed, see above for reason */
+	u16 qlen;
 	u8 quanta_prof_idx;
 	u8 tso_ena;
 	u16 tso_qnum;

-- 
2.47.0.265.g4ca455297942