From: Daniel Borkmann <daniel@iogearbox•net>
To: Alexei Starovoitov <ast@plumgrid•com>,
"Devon H. O'Dell" <dho@fastly•com>
Cc: davem@davemloft•net, edumazet@google•com, netdev@vger•kernel.org
Subject: Re: [PATCH net-next] bpf, skb_do_redirect: clear sender_cpu before xmit
Date: Fri, 09 Oct 2015 19:33:14 +0200 [thread overview]
Message-ID: <5617FA5A.9090406@iogearbox.net> (raw)
In-Reply-To: <561727D5.2070001@plumgrid.com>
On 10/09/2015 04:35 AM, Alexei Starovoitov wrote:
> On 10/8/15 5:50 PM, Devon H. O'Dell wrote:
>>> with the amount of skb_sender_cpu_clear() all over the code base
>>> >I wonder whether there is a better solution to all of these.
>> I think there is. We found that splitting the union of sender_cpu and
>> napi_id solved the issue for us. In general, I think this is an OK
>> solution as long as the following hold:
>>
>> * skbs are always allocated via kzalloc
>> * out -> out cloned skbs are always cloned on the same CPU
>> * an extra four bytes in skbuff isn't a bad thing
>
> I'm pretty sure extending sk_buff for this is not acceptable.
+1, I agree.
> I was thinking may be we can use sign bit to distinguish between
> napi_id and sender_cpu.
> Like:
> if ((int)skb->sender_cpu >= 0)
> skb->sender_cpu = - (raw_smp_processor_id() + 1);
> and inside get_xps_queue() use it only if it's negative.
> Then we can remove skb_sender_cpu_clear() from everywhere.
> Adding a check to napi_hash_add() to make sure that napi_id is not
> negative is probably ok too.
> Thoughts?
I think this doesn't make it any more maintainable.
skb_sender_cpu_clear(), one can at least git-grep to easily find
out and review call-sites in the code. There are various members
already used differently depending on the context.
Thanks,
Daniel
next prev parent reply other threads:[~2015-10-09 17:33 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-07 8:16 [PATCH net-next] bpf, skb_do_redirect: clear sender_cpu before xmit Daniel Borkmann
2015-10-07 15:46 ` Alexei Starovoitov
2015-10-09 0:50 ` Devon H. O'Dell
2015-10-09 2:35 ` Alexei Starovoitov
2015-10-09 16:40 ` Devon H. O'Dell
2015-10-10 3:11 ` Alexei Starovoitov
2015-10-09 17:33 ` Daniel Borkmann [this message]
2015-10-10 3:19 ` Alexei Starovoitov
2015-10-10 4:38 ` Eric Dumazet
2015-10-10 4:55 ` Alexei Starovoitov
2015-10-10 4:56 ` Alexei Starovoitov
2015-10-10 17:12 ` Eric Dumazet
2015-11-16 18:07 ` Eric Dumazet
2015-10-08 12:07 ` David Miller
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