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Date: Tue, 3 Jul 2018 14:21:48 +0800
From: Li RongQing <roy.qing.li@...il.com>
To: David Miller <davem@...emloft.net>
Cc: lirongqing@...du.com, netdev@...r.kernel.org,
eric.dumazet@...il.com
Subject: Re: [PATCH][net-next] net: increase MAX_GRO_SKBS to 64
On 7/2/18, David Miller <davem@...emloft.net> wrote:
> From: Li RongQing <lirongqing@...du.com>
> Date: Mon, 2 Jul 2018 19:41:43 +0800
>
>> After 07d78363dcffd [net: Convert NAPI gro list into a small hash table]
>> there is 8 hash buckets, which allow more flows to be held for merging.
>>
>> keep each as original list length, so increase MAX_GRO_SKBS to 64
>>
>> Signed-off-by: Li RongQing <lirongqing@...du.com>
>
> I would like to hear some feedback from Eric, 64 might be too big.
>
How about the below change?
commit 6270b973a973b2944fedb4b5f9926ed3e379d0c2 (HEAD -> master)
Author: Li RongQing <lirongqing@...du.com>
Date: Mon Jul 2 19:08:37 2018 +0800
net: limit each hash list length to MAX_GRO_SKBS
After 07d78363dcffd [net: Convert NAPI gro list into a small hash table]
there is 8 hash buckets, which allows more flows to be held for merging.
but MAX_GRO_SKBS, the total held skb for merging, is 8 skb still, limit
the hash table performance.
keep MAX_GRO_SKBS as 8 skb, but limit each hash list length to 8 skb, not
the total 8 skb
Signed-off-by: Li RongQing <lirongqing@...du.com>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8bf8d6149f79..09d7764a8917 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -324,6 +324,7 @@ struct napi_struct {
#endif
struct net_device *dev;
struct list_head gro_hash[GRO_HASH_BUCKETS];
+ int list_len[GRO_HASH_BUCKETS];
struct sk_buff *skb;
struct hrtimer timer;
struct list_head dev_list;
diff --git a/net/core/dev.c b/net/core/dev.c
index 08d58e0debe5..3cf3c6676cb3 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -149,7 +149,6 @@
#include "net-sysfs.h"
-/* Instead of increasing this, you should create a hash table. */
#define MAX_GRO_SKBS 8
/* This should be increased if a protocol with a bigger head is added. */
@@ -4989,10 +4988,11 @@ static int napi_gro_complete(struct sk_buff *skb)
return netif_receive_skb_internal(skb);
}
-static void __napi_gro_flush_chain(struct napi_struct *napi, struct
list_head *head,
+static void __napi_gro_flush_chain(struct napi_struct *napi, int index,
bool flush_old)
{
struct sk_buff *skb, *p;
+ struct list_head *head = &napi->gro_hash[index];
list_for_each_entry_safe_reverse(skb, p, head, list) {
if (flush_old && NAPI_GRO_CB(skb)->age == jiffies)
@@ -5000,6 +5000,7 @@ static void __napi_gro_flush_chain(struct
napi_struct *napi, struct list_head *h
list_del_init(&skb->list);
napi_gro_complete(skb);
napi->gro_count--;
+ napi->list_len[index]--;
}
}
@@ -5011,11 +5012,8 @@ void napi_gro_flush(struct napi_struct *napi,
bool flush_old)
{
int i;
- for (i = 0; i < GRO_HASH_BUCKETS; i++) {
- struct list_head *head = &napi->gro_hash[i];
-
- __napi_gro_flush_chain(napi, head, flush_old);
- }
+ for (i = 0; i < GRO_HASH_BUCKETS; i++)
+ __napi_gro_flush_chain(napi, i, flush_old);
}
EXPORT_SYMBOL(napi_gro_flush);
@@ -5095,27 +5093,13 @@ static void gro_pull_from_frag0(struct sk_buff
*skb, int grow)
}
}
-static void gro_flush_oldest(struct napi_struct *napi)
+static void gro_flush_oldest(struct list_head *head)
{
struct sk_buff *oldest = NULL;
- unsigned long age = jiffies;
- int i;
- for (i = 0; i < GRO_HASH_BUCKETS; i++) {
- struct list_head *head = &napi->gro_hash[i];
- struct sk_buff *skb;
+ oldest = list_last_entry(head, struct sk_buff, list);
- if (list_empty(head))
- continue;
-
- skb = list_last_entry(head, struct sk_buff, list);
- if (!oldest || time_before(NAPI_GRO_CB(skb)->age, age)) {
- oldest = skb;
- age = NAPI_GRO_CB(skb)->age;
- }
- }
-
- /* We are called with napi->gro_count >= MAX_GRO_SKBS, so this is
+ /* We are called with head length >= MAX_GRO_SKBS, so this is
* impossible.
*/
if (WARN_ON_ONCE(!oldest))
@@ -5138,6 +5122,7 @@ static enum gro_result dev_gro_receive(struct
napi_struct *napi, struct sk_buff
enum gro_result ret;
int same_flow;
int grow;
+ u32 hash = skb_get_hash_raw(skb) & (GRO_HASH_BUCKETS - 1);
if (netif_elide_gro(skb->dev))
goto normal;
@@ -5196,6 +5181,7 @@ static enum gro_result dev_gro_receive(struct
napi_struct *napi, struct sk_buff
list_del_init(&pp->list);
napi_gro_complete(pp);
napi->gro_count--;
+ napi->list_len[hash]--;
}
if (same_flow)
@@ -5204,10 +5190,11 @@ static enum gro_result dev_gro_receive(struct
napi_struct *napi, struct sk_buff
if (NAPI_GRO_CB(skb)->flush)
goto normal;
- if (unlikely(napi->gro_count >= MAX_GRO_SKBS)) {
- gro_flush_oldest(napi);
+ if (unlikely(napi->list_len[hash] >= MAX_GRO_SKBS)) {
+ gro_flush_oldest(gro_head);
} else {
napi->gro_count++;
+ napi->list_len[hash]++;
}
NAPI_GRO_CB(skb)->count = 1;
NAPI_GRO_CB(skb)->age = jiffies;
@@ -5844,8 +5831,10 @@ void netif_napi_add(struct net_device *dev,
struct napi_struct *napi,
hrtimer_init(&napi->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED);
napi->timer.function = napi_watchdog;
napi->gro_count = 0;
- for (i = 0; i < GRO_HASH_BUCKETS; i++)
+ for (i = 0; i < GRO_HASH_BUCKETS; i++) {
INIT_LIST_HEAD(&napi->gro_hash[i]);
+ napi->list_len[i] = 0;
+ }
napi->skb = NULL;
napi->poll = poll;
if (weight > NAPI_POLL_WEIGHT)
@@ -5887,6 +5876,7 @@ static void flush_gro_hash(struct napi_struct *napi)
list_for_each_entry_safe(skb, n, &napi->gro_hash[i], list)
kfree_skb(skb);
+ napi->list_len[i] = 0;
}
}
-R
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