netdev - Re: [PATCH 2/2 net-next] net: move qdisc ingress filtering code where it belongs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 12 May 2015 15:27:03 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Pablo Neira Ayuso <pablo@...filter.org>,
	Eric Dumazet <eric.dumazet@...il.com>
CC:	Alexei Starovoitov <ast@...mgrid.com>, netdev@...r.kernel.org,
	davem@...emloft.net, jhs@...atatu.com
Subject: Re: [PATCH 2/2 net-next] net: move qdisc ingress filtering code where
 it belongs

Hi Pablo,

On 05/12/2015 02:55 PM, Pablo Neira Ayuso wrote:
> On Mon, May 11, 2015 at 04:30:38PM -0700, Eric Dumazet wrote:
>> On Mon, 2015-05-11 at 16:02 -0700, Alexei Starovoitov wrote:
>>> On 5/11/15 7:35 AM, Eric Dumazet wrote:
>>>>
>>>> -static inline int deliver_skb(struct sk_buff *skb,
>>>> +static noinline int deliver_skb(struct sk_buff *skb,
>>>>    			      struct packet_type *pt_prev,
>>>>    			      struct net_device *orig_dev)
>>>
>>> have tried the above only and didn't see any difference
>>> for simple 'netif_receive + drop in ip_rcv' test.
>>> Not sure whether it's actually worth doing. I would leave it as-is.
>>
>> Yes, this was probably too aggressive.
>
> I tested this noinline patch and I got a bit less performance here in
> my 32K i-cache testbed.
>
>> unlikely() or static_key_false() are no moving code away enough, whole
>> function including unused code pollutes icache.
>>
>> Code size increased a lot, while L1/L2 caches on cpu are about the same
>> than 6 years ago.
>
> OK, so that explains why I'm getting more performance with the patch
> that move the qdisc ingress code using the indirection, since that
> helped to move code away, right?
>
> BTW, looking at the emails, Daniel said:
>
> [...]
>> After your patch set:
>>
>> Samples: 50K of event 'cycles:k', Event count (approx.): 45160667741
>> +   40.49%  kpktgend_0  [kernel.kallsyms]  [k] __netif_receive_skb_core
>> +   31.21%  kpktgend_0  [kernel.kallsyms]  [k] kfree_skb
>> +    6.94%  kpktgend_0  [pktgen]           [k] pktgen_thread_worker
>> +    6.63%  kpktgend_0  [kernel.kallsyms]  [k] netif_receive_skb_internal
>> +    6.63%  kpktgend_0  [kernel.kallsyms]  [k] ip_rcv
>> +    3.30%  kpktgend_0  [kernel.kallsyms]  [k] netif_receive_skb_sk
>> +    3.30%  kpktgend_0  [kernel.kallsyms]  [k] __netif_receive_skb
>> +    0.96%  kpktgend_0  [kernel.kallsyms]  [k] __local_bh_enable_ip
>> +    0.37%  kpktgend_0  [kernel.kallsyms]  [k] kthread_should_stop
>> +    0.03%  kpktgend_0  [kernel.kallsyms]  [k] _cond_resched
>>
>> For *all* three, I reliably get ~40.0 Mpps with the benchmark.
>
> @Daniel, Alexei: Are you getting the same numbers with the indirection?

The above I tested was basically your set from here on top of net-next
when ingress is disabled. It didn't show an effect (similarly as the
printk bloat test patch on my side). So, judging from your observations,
the printk bloat would also make things slower on your side, right?

> What's the i-cache size in your testbed?

For the Xeon E3-1240, I get (via lscpu):

L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              8192K

Best,
Daniel
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html