After searching for a protocol handler in dev_gro_receive, checking for
failure is redundant. Skip the failure code after finding the
corresponding handler.
Signed-off-by: Richard Gobert <[email protected]>
---
net/core/gro.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/core/gro.c b/net/core/gro.c
index bc9451743307..a4e1b5a5be64 100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -522,13 +522,13 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
pp = INDIRECT_CALL_INET(ptype->callbacks.gro_receive,
ipv6_gro_receive, inet_gro_receive,
&gro_list->list, skb);
- break;
+ rcu_read_unlock();
+ goto found;
}
rcu_read_unlock();
+ goto normal;
- if (&ptype->list == head)
- goto normal;
-
+found:
if (PTR_ERR(pp) == -EINPROGRESS) {
ret = GRO_CONSUMED;
goto ok;
--
2.20.1
On Mon, 24 Oct 2022 07:17:49 +0200 Richard Gobert wrote:
> After searching for a protocol handler in dev_gro_receive, checking for
> failure is redundant. Skip the failure code after finding the
> corresponding handler.
Why does it matter? You see a measurable perf win?
Please fix the data on your system when you repost.
> Why does it matter? You see a measurable perf win?
In the common case, we will exit the loop with a break,
so this patch eliminates an unnecessary check.
On some architectures this optimization might be done
automatically by the compiler, but I think it will be better
to make it explicit here. Although on x86 this optimization
happens automatically, I noticed that on my build target
(ARM/GCC) this does change the binary.
On Wed, Nov 2, 2022 at 9:46 AM Richard Gobert <[email protected]> wrote:
>
> > Why does it matter? You see a measurable perf win?
>
> In the common case, we will exit the loop with a break,
> so this patch eliminates an unnecessary check.
>
> On some architectures this optimization might be done
> automatically by the compiler, but I think it will be better
> to make it explicit here. Although on x86 this optimization
> happens automatically, I noticed that on my build target
> (ARM/GCC) this does change the binary.
What about taking this as an opportunity to reduce the indentation
level by one tab ?
Untested patch:
diff --git a/net/core/gro.c b/net/core/gro.c
index bc9451743307bc380cca96ae6995aa0a3b83d185..ddfe92c9a5e869d241931b72d6b3426a0e858468
100644
--- a/net/core/gro.c
+++ b/net/core/gro.c
@@ -491,43 +491,44 @@ static enum gro_result dev_gro_receive(struct
napi_struct *napi, struct sk_buff
list_for_each_entry_rcu(ptype, head, list) {
if (ptype->type != type || !ptype->callbacks.gro_receive)
continue;
+ goto found_ptype;
+ }
+ rcu_read_unlock();
+ goto normal;
- skb_set_network_header(skb, skb_gro_offset(skb));
- skb_reset_mac_len(skb);
- BUILD_BUG_ON(sizeof_field(struct napi_gro_cb, zeroed)
!= sizeof(u32));
- BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed),
- sizeof(u32))); /* Avoid slow
unaligned acc */
- *(u32 *)&NAPI_GRO_CB(skb)->zeroed = 0;
- NAPI_GRO_CB(skb)->flush = skb_has_frag_list(skb);
- NAPI_GRO_CB(skb)->is_atomic = 1;
- NAPI_GRO_CB(skb)->count = 1;
- if (unlikely(skb_is_gso(skb))) {
- NAPI_GRO_CB(skb)->count = skb_shinfo(skb)->gso_segs;
- /* Only support TCP at the moment. */
- if (!skb_is_gso_tcp(skb))
- NAPI_GRO_CB(skb)->flush = 1;
- }
-
- /* Setup for GRO checksum validation */
- switch (skb->ip_summed) {
- case CHECKSUM_COMPLETE:
- NAPI_GRO_CB(skb)->csum = skb->csum;
- NAPI_GRO_CB(skb)->csum_valid = 1;
- break;
- case CHECKSUM_UNNECESSARY:
- NAPI_GRO_CB(skb)->csum_cnt = skb->csum_level + 1;
- break;
- }
+found_ptype:
+ skb_set_network_header(skb, skb_gro_offset(skb));
+ skb_reset_mac_len(skb);
+ BUILD_BUG_ON(sizeof_field(struct napi_gro_cb, zeroed) != sizeof(u32));
+ BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed),
+ sizeof(u32))); /* Avoid slow unaligned acc */
+ *(u32 *)&NAPI_GRO_CB(skb)->zeroed = 0;
+ NAPI_GRO_CB(skb)->flush = skb_has_frag_list(skb);
+ NAPI_GRO_CB(skb)->is_atomic = 1;
+ NAPI_GRO_CB(skb)->count = 1;
+ if (unlikely(skb_is_gso(skb))) {
+ NAPI_GRO_CB(skb)->count = skb_shinfo(skb)->gso_segs;
+ /* Only support TCP at the moment. */
+ if (!skb_is_gso_tcp(skb))
+ NAPI_GRO_CB(skb)->flush = 1;
+ }
- pp = INDIRECT_CALL_INET(ptype->callbacks.gro_receive,
- ipv6_gro_receive, inet_gro_receive,
- &gro_list->list, skb);
+ /* Setup for GRO checksum validation */
+ switch (skb->ip_summed) {
+ case CHECKSUM_COMPLETE:
+ NAPI_GRO_CB(skb)->csum = skb->csum;
+ NAPI_GRO_CB(skb)->csum_valid = 1;
+ break;
+ case CHECKSUM_UNNECESSARY:
+ NAPI_GRO_CB(skb)->csum_cnt = skb->csum_level + 1;
break;
}
- rcu_read_unlock();
- if (&ptype->list == head)
- goto normal;
+ pp = INDIRECT_CALL_INET(ptype->callbacks.gro_receive,
+ ipv6_gro_receive, inet_gro_receive,
+ &gro_list->list, skb);
+
+ rcu_read_unlock();
if (PTR_ERR(pp) == -EINPROGRESS) {
ret = GRO_CONSUMED;
On Wed, Nov 2, 2022 at 11:20 AM Eric Dumazet <[email protected]> wrote:
>
> On Wed, Nov 2, 2022 at 9:46 AM Richard Gobert <[email protected]> wrote:
> >
> > > Why does it matter? You see a measurable perf win?
> >
> > In the common case, we will exit the loop with a break,
> > so this patch eliminates an unnecessary check.
> >
> > On some architectures this optimization might be done
> > automatically by the compiler, but I think it will be better
> > to make it explicit here. Although on x86 this optimization
> > happens automatically, I noticed that on my build target
> > (ARM/GCC) this does change the binary.
>
> What about taking this as an opportunity to reduce the indentation
> level by one tab ?
>
> Untested patch:
>
> diff --git a/net/core/gro.c b/net/core/gro.c
> index bc9451743307bc380cca96ae6995aa0a3b83d185..ddfe92c9a5e869d241931b72d6b3426a0e858468
> 100644
> --- a/net/core/gro.c
> +++ b/net/core/gro.c
> @@ -491,43 +491,44 @@ static enum gro_result dev_gro_receive(struct
> napi_struct *napi, struct sk_buff
> list_for_each_entry_rcu(ptype, head, list) {
> if (ptype->type != type || !ptype->callbacks.gro_receive)
> continue;
> + goto found_ptype;
> + }
> + rcu_read_unlock();
> + goto normal;
Or even better:
list_for_each_entry_rcu(ptype, head, list) {
if (ptype->type == type && ptype->callbacks.gro_receive)
goto found_ptype;
}
rcu_read_unlock();
goto normal;