2024-01-26 00:34:36

by Stephen Hemminger

Subject: [PATCH] net/tun: use reciprocal_scale

Use the inline function reciprocal_scale rather than open coding
the scale optimization. Also, remove unnecessary initializations.
Resulting compiled code is unchanged (according to godbolt).

Signed-off-by: Stephen Hemminger <[email protected]>
---
drivers/net/tun.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 4a4f8c8e79fa..e335ece47dec 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -54,6 +54,7 @@
#include <linux/if_tun.h>
#include <linux/if_vlan.h>
#include <linux/crc32.h>
+#include <linux/math.h>
#include <linux/nsproxy.h>
#include <linux/virtio_net.h>
#include <linux/rcupdate.h>
@@ -523,8 +524,7 @@ static inline void tun_flow_save_rps_rxhash(struct tun_flow_entry *e, u32 hash)
static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb)
{
struct tun_flow_entry *e;
- u32 txq = 0;
- u32 numqueues = 0;
+ u32 txq, numqueues;

numqueues = READ_ONCE(tun->numqueues);

@@ -534,8 +534,7 @@ static u16 tun_automq_select_queue(struct tun_struct *tun, struct sk_buff *skb)
tun_flow_save_rps_rxhash(e, txq);
txq = e->queue_index;
} else {
- /* use multiply and shift instead of expensive divide */
- txq = ((u64)txq * numqueues) >> 32;
+ txq = reciprocal_scale(txq, numqueues);
}

return txq;
--
2.43.0

2024-01-27 16:06:35

by Willem de Bruijn

Subject: Re: [PATCH] net/tun: use reciprocal_scale

Stephen Hemminger wrote:
> Use the inline function reciprocal_scale rather than open coding
> the scale optimization. Also, remove unnecessary initializations.
> Resulting compiled code is unchanged (according to godbolt).
>
> Signed-off-by: Stephen Hemminger <[email protected]>

Targeting net-next

Reviewed-by: Willem de Bruijn <[email protected]>

2024-01-29 03:02:23

by Jason Wang

Subject: Re: [PATCH] net/tun: use reciprocal_scale

On Fri, Jan 26, 2024 at 8:26 AM Stephen Hemminger
<[email protected]> wrote:
>
> Use the inline function reciprocal_scale rather than open coding
> the scale optimization. Also, remove unnecessary initializations.
> Resulting compiled code is unchanged (according to godbolt).
>
> Signed-off-by: Stephen Hemminger <[email protected]>

Acked-by: Jason Wang <[email protected]>

Thanks

2024-01-30 11:11:38

by patchwork-bot+netdevbpf

Subject: Re: [PATCH] net/tun: use reciprocal_scale

Hello:

This patch was applied to netdev/net-next.git (main)
by Paolo Abeni <[email protected]>:

On Thu, 25 Jan 2024 16:25:11 -0800 you wrote:
> Use the inline function reciprocal_scale rather than open coding
> the scale optimization. Also, remove unnecessary initializations.
> Resulting compiled code is unchanged (according to godbolt).
>
> Signed-off-by: Stephen Hemminger <[email protected]>
> ---
> drivers/net/tun.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)

Here is the summary with links:
- net/tun: use reciprocal_scale
https://git.kernel.org/netdev/net-next/c/3f3ebe536208

You are awesome, thank you!
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