* [net-next] be2net: use shift instead of expensive divide
@ 2017-08-29 3:18 Zhang Shengju
2017-08-29 3:44 ` Joe Perches
2017-08-29 4:25 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Zhang Shengju @ 2017-08-29 3:18 UTC (permalink / raw)
To: sathya.perla, ajit.khaparde, sriharsha.basavapatna, netdev
Replace shift instead of expensive divide.
Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
---
drivers/net/ethernet/emulex/benet/be_main.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/net/ethernet/emulex/benet/be_main.c b/drivers/net/ethernet/emulex/benet/be_main.c
index 319eee3..e06094f 100644
--- a/drivers/net/ethernet/emulex/benet/be_main.c
+++ b/drivers/net/ethernet/emulex/benet/be_main.c
@@ -2455,7 +2455,7 @@ static struct be_rx_compl_info *be_rx_compl_get(struct be_rx_obj *rxo)
/* For checking the valid bit it is Ok to use either definition as the
* valid bit is at the same position in both v0 and v1 Rx compl */
- if (compl->dw[offsetof(struct amap_eth_rx_compl_v1, valid) / 32] == 0)
+ if (compl->dw[offsetof(struct amap_eth_rx_compl_v1, valid) >> 5] == 0)
return NULL;
rmb();
@@ -2486,7 +2486,7 @@ static struct be_rx_compl_info *be_rx_compl_get(struct be_rx_obj *rxo)
}
/* As the compl has been parsed, reset it; we wont touch it again */
- compl->dw[offsetof(struct amap_eth_rx_compl_v1, valid) / 32] = 0;
+ compl->dw[offsetof(struct amap_eth_rx_compl_v1, valid) >> 5] = 0;
queue_tail_inc(&rxo->cq);
return rxcp;
@@ -2590,7 +2590,7 @@ static struct be_tx_compl_info *be_tx_compl_get(struct be_tx_obj *txo)
struct be_tx_compl_info *txcp = &txo->txcp;
struct be_eth_tx_compl *compl = queue_tail_node(tx_cq);
- if (compl->dw[offsetof(struct amap_eth_tx_compl, valid) / 32] == 0)
+ if (compl->dw[offsetof(struct amap_eth_tx_compl, valid) >> 5] == 0)
return NULL;
/* Ensure load ordering of valid bit dword and other dwords below */
@@ -2600,7 +2600,7 @@ static struct be_tx_compl_info *be_tx_compl_get(struct be_tx_obj *txo)
txcp->status = GET_TX_COMPL_BITS(status, compl);
txcp->end_index = GET_TX_COMPL_BITS(wrb_index, compl);
- compl->dw[offsetof(struct amap_eth_tx_compl, valid) / 32] = 0;
+ compl->dw[offsetof(struct amap_eth_tx_compl, valid) >> 5] = 0;
queue_tail_inc(tx_cq);
return txcp;
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [net-next] be2net: use shift instead of expensive divide
2017-08-29 3:18 [net-next] be2net: use shift instead of expensive divide Zhang Shengju
@ 2017-08-29 3:44 ` Joe Perches
2017-08-29 4:25 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Joe Perches @ 2017-08-29 3:44 UTC (permalink / raw)
To: Zhang Shengju, sathya.perla, ajit.khaparde,
sriharsha.basavapatna, netdev
On Tue, 2017-08-29 at 11:18 +0800, Zhang Shengju wrote:
> Replace shift instead of expensive divide.
This change is mostly pointless.
Any half-way decent compiler should produce the same object.
gcc emits the same object with the old code.
The AMAP_GET_BITS macro uses the "offsetof(struct, member) / 32"
style too.
> diff --git a/drivers/net/ethernet/emulex/benet/be_main.c b/drivers/net/ethernet/emulex/benet/be_main.c
[]
> @@ -2455,7 +2455,7 @@ static struct be_rx_compl_info *be_rx_compl_get(struct be_rx_obj *rxo)
>
> /* For checking the valid bit it is Ok to use either definition as the
> * valid bit is at the same position in both v0 and v1 Rx compl */
> - if (compl->dw[offsetof(struct amap_eth_rx_compl_v1, valid) / 32] == 0)
> + if (compl->dw[offsetof(struct amap_eth_rx_compl_v1, valid) >> 5] == 0)
etc...
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [net-next] be2net: use shift instead of expensive divide
2017-08-29 3:18 [net-next] be2net: use shift instead of expensive divide Zhang Shengju
2017-08-29 3:44 ` Joe Perches
@ 2017-08-29 4:25 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2017-08-29 4:25 UTC (permalink / raw)
To: zhangshengju; +Cc: sathya.perla, ajit.khaparde, sriharsha.basavapatna, netdev
From: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Date: Tue, 29 Aug 2017 11:18:39 +0800
> Replace shift instead of expensive divide.
>
> Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
The divide is more easier to understand, and it costs the same
as a shift if the types are unsigned.
I'm not applying silly changes like this which actually make
the code worse off, sorry.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-08-29 4:25 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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