Date: Sun, 03 Jun 2012 08:33:53 -0400 From: Andrew Gallatin <gallatin@myri.com> To: Kevin Oberman <kob6558@gmail.com> Cc: Lawrence Stewart <lstewart@freebsd.org>, Andrew Gallatin <gallatin@cs.duke.edu>, freebsd-net@freebsd.org Subject: Re: Major performance hit with ToS setting Message-ID: <4FCB59B1.2050908@myri.com> In-Reply-To: <CAN6yY1v08qk2VhXFg0Qiz-pMM6md2c_E_kEvA-oqbxuvSN1JDg@mail.gmail.com> References: <CAN6yY1sLxFJ18ANO7nQqLetnJiT-K6pHC-X3yT1dWuWGa0VLUg@mail.gmail.com> <4FBF88CE.20209@cs.duke.edu> <CAN6yY1v%2Bvf=SW7WDGHxCkJtOdj8K3f450jNxFWK_Jc%2B-pFg0nA@mail.gmail.com> <4FC82D6C.4050309@freebsd.org> <CAN6yY1v08qk2VhXFg0Qiz-pMM6md2c_E_kEvA-oqbxuvSN1JDg@mail.gmail.com>
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On 06/03/12 01:18, Kevin Oberman wrote: > What can I say but that you are right. When I looked at the interface > stats I found that the link overflow drops were through the roof! This > confuses me a bit since the traffic is outbound and I woudl assume Indeed, link overflow is incoming traffic that was dropped due to lack of rx resources. If you have flow control disabled, it is drops simply due to lack of space in the rx fifo. If you have flow control enabled, link overflow can include drops due to lack of host rx buffers as well. For primarily WAN traffic, we suggest that flow control be disabled (it is enabled by default). With f/c disabled, drops due to lack of rx buffers are counted as dropped_no_[big|small]_buffer At any rate, it is surprising to see link overflow increase on an outgoing unidirectional test. Is there other incoming traffic that you might not have been aware of? The only really unlikely thing I can think of is if something is buffering tens of thousands of acks and dumping them all at once. Drew
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