* [PATCH] net/tun: use reciprocal_scale
@ 2024-01-26 0:25 Stephen Hemminger
2024-01-27 16:06 ` Willem de Bruijn
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Stephen Hemminger @ 2024-01-26 0:25 UTC (permalink / raw)
To: netdev
Cc: Stephen Hemminger, Willem de Bruijn, Jason Wang, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, open list
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 <stephen@networkplumber.org>
---
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] net/tun: use reciprocal_scale
2024-01-26 0:25 [PATCH] net/tun: use reciprocal_scale Stephen Hemminger
@ 2024-01-27 16:06 ` Willem de Bruijn
2024-01-29 3:01 ` Jason Wang
2024-01-30 11:10 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Willem de Bruijn @ 2024-01-27 16:06 UTC (permalink / raw)
To: Stephen Hemminger, netdev
Cc: Stephen Hemminger, Willem de Bruijn, Jason Wang, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, open list
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 <stephen@networkplumber.org>
Targeting net-next
Reviewed-by: Willem de Bruijn <willemb@google.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] net/tun: use reciprocal_scale
2024-01-26 0:25 [PATCH] net/tun: use reciprocal_scale Stephen Hemminger
2024-01-27 16:06 ` Willem de Bruijn
@ 2024-01-29 3:01 ` Jason Wang
2024-01-30 11:10 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Jason Wang @ 2024-01-29 3:01 UTC (permalink / raw)
To: Stephen Hemminger
Cc: netdev, Willem de Bruijn, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, open list
On Fri, Jan 26, 2024 at 8:26 AM Stephen Hemminger
<stephen@networkplumber.org> 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 <stephen@networkplumber.org>
Acked-by: Jason Wang <jasowang@redhat.com>
Thanks
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] net/tun: use reciprocal_scale
2024-01-26 0:25 [PATCH] net/tun: use reciprocal_scale Stephen Hemminger
2024-01-27 16:06 ` Willem de Bruijn
2024-01-29 3:01 ` Jason Wang
@ 2024-01-30 11:10 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2024-01-30 11:10 UTC (permalink / raw)
To: Stephen Hemminger
Cc: netdev, willemdebruijn.kernel, jasowang, davem, edumazet, kuba,
pabeni, linux-kernel
Hello:
This patch was applied to netdev/net-next.git (main)
by Paolo Abeni <pabeni@redhat.com>:
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 <stephen@networkplumber.org>
> ---
> 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!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-01-26 0:25 [PATCH] net/tun: use reciprocal_scale Stephen Hemminger
2024-01-27 16:06 ` Willem de Bruijn
2024-01-29 3:01 ` Jason Wang
2024-01-30 11:10 ` patchwork-bot+netdevbpf
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