netdev - Re: [PATCH v4 net-next 2/3] net/udp: Add 4-tuple hash list basis

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Message-ID: <2888bb8f-1ee4-4342-968f-82573d583709@linux.alibaba.com>
Date: Wed, 16 Oct 2024 14:30:57 +0800
From: Philo Lu <lulie@...ux.alibaba.com>
To: Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc: willemdebruijn.kernel@...il.com, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, dsahern@...nel.org,
 antony.antony@...unet.com, steffen.klassert@...unet.com,
 linux-kernel@...r.kernel.org, dust.li@...ux.alibaba.com,
 jakub@...udflare.com, fred.cc@...baba-inc.com,
 yubing.qiuyubing@...baba-inc.com
Subject: Re: [PATCH v4 net-next 2/3] net/udp: Add 4-tuple hash list basis



On 2024/10/14 18:07, Paolo Abeni wrote:
> Hi,
> 
> On 10/12/24 03:29, Philo Lu wrote:
>> @@ -3480,13 +3486,14 @@ static struct udp_table __net_init 
>> *udp_pernet_table_alloc(unsigned int hash_ent
>>       if (!udptable)
>>           goto out;
>> -    slot_size = sizeof(struct udp_hslot) + sizeof(struct 
>> udp_hslot_main);
>> +    slot_size = 2 * sizeof(struct udp_hslot) + sizeof(struct 
>> udp_hslot_main);
>>       udptable->hash = vmalloc_huge(hash_entries * slot_size,
>>                         GFP_KERNEL_ACCOUNT);
> 
> I'm sorry for the late feedback.
> 
> I think it would be better to make the hash4 infra a no op (no lookup, 
> no additional memory used) for CONFIG_BASE_SMALL=y builds.
> 

Got it. There are 2 affected structs, udp_hslot and udp_sock. They (as 
well as related helpers like udp4_hash4) can be wrapped with 
CONFIG_BASE_SMALL, and then we can enable BASE_SMALL to eliminate 
additional overhead of hash4.

```
+struct udp_hslot_main {
+	struct udp_hslot	hslot; /* must be the first member */
+#if !IS_ENABLED(CONFIG_BASE_SMALL)
+	u32			hash4_cnt;
+#endif
+} __aligned(2 * sizeof(long));


@@ -56,6 +56,12 @@ struct udp_sock {
  	int		 pending;	/* Any pending frames ? */
  	__u8		 encap_type;	/* Is this an Encapsulation socket? */

+#if !IS_ENABLED(CONFIG_BASE_SMALL)
+	/* For UDP 4-tuple hash */
+	__u16 udp_lrpa_hash;
+	struct hlist_node udp_lrpa_node;
+#endif
+
```

> It would be great if you could please share some benchmark showing the 
> raw max receive PPS performances for unconnected sockets, with and 
> without this series applied, to ensure this does not cause any real 
> regression for such workloads.
> 

Tested using sockperf tp with default msgsize (14B), 3 times for w/ and 
w/o the patch set, and results show no obvious difference:

[msg/sec]  test1    test2    test3    mean
w/o patch  514,664  519,040  527,115  520.3k
w/  patch  516,863  526,337  527,195  523.5k (+0.6%)

Thank you for review, Paolo.
-- 
Philo