Date: Mon, 7 May 2012 22:16:55 -0700 From: Jack Vogel <jfvogel@gmail.com> To: Juli Mallett <jmallett@freebsd.org> Cc: freebsd-net@freebsd.org, Vijay Singh <vijju.singh@gmail.com> Subject: Re: What does adapter->stats.mpc[] report for ixgbe? Message-ID: <CAFOYbcm8q62NFfW5W_WsPrToiaUY0swbh-S1jC4MqSQrg%2Butrg@mail.gmail.com> In-Reply-To: <CACVs6=_6vsSi547UTSB7fjPK_E-yWkFZ_1Edt79=ym7rGKTQQQ@mail.gmail.com> References: <CALCNsJSuG2gUyOZu-PkzaFqt0Vf_aymLf3Jc=czCzW=q9E4t8w@mail.gmail.com> <CAFOYbcmQZ0hfWasZDKk9N1v6z_R3KobkURE48M-2Wjyx%2B7j67w@mail.gmail.com> <CACVs6=9kNzB6sDXE1jPKKQCR8LD7h98ME7hFrKqtasUf-RCBwQ@mail.gmail.com> <CAFOYbc=O4w2H8FN8t0pQiJKp2fNMGOtsN5TfZJ3GoX4YnijTcw@mail.gmail.com> <CALCNsJREq13sqNoRtH2uuvjc4BVPUe7Kc5o5N2V7u3OR%2BqkxiA@mail.gmail.com> <CACVs6=_6vsSi547UTSB7fjPK_E-yWkFZ_1Edt79=ym7rGKTQQQ@mail.gmail.com>
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Juli is correct, the FIFO is not partitioned by the driver queues as they exist in the current driver, its only seperated into the 3 parts I mentioned. Jack On Mon, May 7, 2012 at 9:55 PM, Juli Mallett <jmallett@freebsd.org> wrote: > On Mon, May 7, 2012 at 9:42 PM, Vijay Singh <vijju.singh@gmail.com> wrote: > >> normal net traffic. But for now in FreeBSD its just one which is divided > >> into 3 parts: TX, RX, and FDIR (flow director). > > > > Jack, does the sw driver control in any way the partitioning of the > > FIFO? I guess enabling 2 hw queues splits the FIFO in half. But > > otherwise does the driver control this in any way? > > I don't believe that multiple queues splits the FIFO (Jack can correct > me if I'm wrong.) This is a small (very small) chunk of low-latency > memory on the NIC itself that is used to store the packets as they > come in off the wire before they are moved to a receive descriptor. > The driver does have a way of partitioning the space between transmit > and receive, look for "PBA" in the drivers. In some cases if you're > doing mostly-transmit or mostly-receive it can be very helpful to > tweak these values, but in the case where you're running out of > receive FIFO space constantly, it's (in my limited experience) more > likely to be a problem with bandwidth or latency between the NIC and > main memory, causing backpressure within the NIC as it tries to move > packets to receive buffers (which are the ones allocated in main, i.e. > host, memory.) >
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