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Date: Wed, 3 Feb 2016 12:59:47 -0500 From: Sowmini Varadhan <sowmini.varadhan@...cle.com> To: Tom Herbert <tom@...bertland.com> Cc: "David S. Miller" <davem@...emloft.net>, Linux Kernel Network Developers <netdev@...r.kernel.org>, Kernel Team <kernel-team@...com> Subject: Re: [PATCH net] net: Allow flow dissector to handle non 4-byte aligned headers On (02/03/16 09:51), Tom Herbert wrote: > > (a) quite noisy > > Try disabling the crash dump. That will improve performance. huh?? there is no crash dump involved. If you meant "disable dump_stack()" sure, I am aware of that, and that is the default behavior of log_unaligned(). I was just trying to be helpful and provide stack traces (I dropped out quite a few, which come from mld, ip_fast_csum() etc, which log_unaligned rate-limits and suppresses by default, btw) (Removing the batteries from my fire-alarm doesnt make the fire go away :-)) > But as we said it's only for tunnels that specifically encapsulate an > ethernet header with aligning it. Many other encapsulations (e.g. > IPIP, GUE, EtherIP,IP/GRE) should be fine. We could take this to IETF > and point out that alignment is still relevant in protocol > development. We can't fix this for GRE or VXLAN at this point, but > maybe there's still hope for VXLAN-GPE or Geneve... good point about taking to ietf, but the list above is not accurate. IP/GRE itself generated a few log_unaligned() warnings for me, I'd have to sift through it carefully - need some time for that.. > Right, but there is a big difference between a performance degradation > and a hard failure. It would at least be nice to know what the > performance hit actually is, if it's acceptable then this would be a > far simpler and much less invasive fix than the alternatives. --Sowmini
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