2018-04-08 18:51 GMT+02:00 David Miller <da...@davemloft.net>:
>
> From: Wenhua Shi <march...@gmail.com>
> Date: Fri, 6 Apr 2018 03:43:39 +0200
>
> > Signed-off-by: Wenhua Shi <march...@gmail.com>
>
> This precondition should be made impossible instead of having to do
> an extra check everywhere that this helper is invoked, many of which
> are in fast paths.
I believe the precondition you said is quite true. In my situation, I
have to disable GSO for some packet and I notice that it leads to a
worse performance (slower than 1Mbps, was almost 800Mbps).
Here's the hook I use on debian 9.4, kernel version 4.9:
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/ip.h>
unsigned int hook_outgoing (
void * priv,
struct sk_buff * skb,
const struct nf_hook_state * state)
{
/* for some reason I have to disable GSO */
skb_gso_reset(skb);
/* After I force sk_can_gso to return false here, the
performance comes back normal. */
// skb->sk->sk_gso_type = ~0;
return NF_ACCEPT;
}
static struct nf_hook_ops hook =
{
.hook = hook_outgoing,
.pf = PF_INET,
.hooknum = NF_INET_POST_ROUTING,
.priority = NF_IP_PRI_LAST,
};
static int __init init_testing(void)
{
nf_register_hook(&hook);
return 0;
}
static void __exit exit_testing(void)
{
nf_unregister_hook(&hook);
}
module_init(init_testing);
module_exit(exit_testing);
Here are the performance measurements.
Without the previous hook:
root@debian-s-1vcpu-1gb-sfo1-01:~/test# iperf -c myanothernormaldebian -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to myanothernormaldebian, TCP port 5001
TCP window size: 255 KByte (default)
------------------------------------------------------------
[ 3] local 192.241.204.XXX port 60528 connected with
104.131.148.XXX port 5001
[ 5] local 192.241.204.XXX port 5001 connected with
104.131.148.XXX port 58576
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 922 MBytes 773 Mbits/sec
[ 5] 0.0-10.1 sec 1.00 GBytes 849 Mbits/sec
And with the previous hook:
root@debian-s-1vcpu-1gb-sfo1-01:~/test# iperf -c myanothernormaldebian -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to myanothernormaldebian, TCP port 5001
TCP window size: 85.0 KByte (default)
------------------------------------------------------------
[ 3] local 192.241.204.XXX port 60530 connected with
104.131.148.XXX port 5001
[ 5] local 192.241.204.XXX port 5001 connected with
104.131.148.XXX port 58578
[ ID] Interval Transfer Bandwidth
[ 5] 0.0-10.2 sec 1.02 GBytes 864 Mbits/sec
[ 3] 0.0-13.5 sec 170 KBytes 103 Kbits/sec
Or it's just because of that I'm disabling the GSO in a wrong way?
