netdev - Re: [PATCH net-next-2.6] net: speedup udp receive path

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Date:	Sat, 01 May 2010 08:14:02 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	hadi@...erus.ca
Cc:	Changli Gao <xiaosuo@...il.com>,
	David Miller <davem@...emloft.net>, therbert@...gle.com,
	shemminger@...tta.com, netdev@...r.kernel.org,
	Eilon Greenstein <eilong@...adcom.com>,
	Brian Bloniarz <bmb@...enacr.com>
Subject: Re: [PATCH net-next-2.6] net: speedup udp receive path

Le samedi 01 mai 2010 à 07:57 +0200, Eric Dumazet a écrit :
> Le vendredi 30 avril 2010 à 20:06 -0400, jamal a écrit :
> 
> > Yes, Nehalem. 
> > RPS off is better (~700Kpp) than RPS on(~650kpps). Are you seeing the
> > same trend on the old hardware?
> > 
> 
> Of course not ! Or else RPS would be useless :(
> 
> I changed your program a bit to use EV_PERSIST, (to avoid epoll_ctl()
> overhead for each packet...)
> 
> RPS off : 220.000 pps 
> 
> RPS on (ee mask) : 700.000 pps  (with a slightly modified tg3 driver)
> 96% of delivered packets

BTW, using ee mask, cpu4 is not used at _all_, even for the user
threads. Scheduler does a bad job IMHO.

Using fe mask, I get all packets (sent at 733311pps by my pktgen
machine), and my CPU0 even has idle time !!!

Limit seems to be around 800.000 pps

------------------------------------------------------------------------------------------------------------------------
   PerfTop:    5616 irqs/sec  kernel:93.9% [1000Hz cycles],  (all, 8 CPUs)
------------------------------------------------------------------------------------------------------------------------

             samples  pcnt function                    DSO
             _______ _____ ___________________________ _______

             3492.00  6.2% __slab_free                 vmlinux
             2334.00  4.2% _raw_spin_lock              vmlinux
             2314.00  4.1% _raw_spin_lock_irqsave      vmlinux
             1807.00  3.2% ip_rcv                      vmlinux
             1605.00  2.9% schedule                    vmlinux
             1474.00  2.6% __netif_receive_skb         vmlinux
             1464.00  2.6% kfree                       vmlinux
             1405.00  2.5% ip_route_input              vmlinux
             1318.00  2.4% __copy_to_user_ll           vmlinux
             1214.00  2.2% __alloc_skb                 vmlinux
             1160.00  2.1% nf_hook_slow                vmlinux
             1020.00  1.8% eth_type_trans              vmlinux
              860.00  1.5% sched_clock_local           vmlinux
              775.00  1.4% read_tsc                    vmlinux
              773.00  1.4% ipt_do_table                vmlinux
              766.00  1.4% _raw_spin_unlock_irqrestore vmlinux
              748.00  1.3% sock_recv_ts_and_drops      vmlinux
              747.00  1.3% ia32_sysenter_target        vmlinux
              740.00  1.3% select_nohz_load_balancer   vmlinux
              644.00  1.2% __kmalloc_track_caller      vmlinux
              596.00  1.1% tg3_read32                  vmlinux
              566.00  1.0% __udp4_lib_lookup           vmlinux




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