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Date: Wed, 09 Sep 2015 12:34:59 -0700 (PDT) From: David Miller <davem@...emloft.net> To: david.vrabel@...rix.com Cc: netdev@...r.kernel.org, xen-devel@...ts.xenproject.org, ian.campbell@...rix.com, wei.liu2@...rix.com Subject: Re: [PATCHv1 net] xen-netback: require fewer guest Rx slots when not using GSO From: David Vrabel <david.vrabel@...rix.com> Date: Tue, 8 Sep 2015 14:25:14 +0100 > Commit f48da8b14d04ca87ffcffe68829afd45f926ec6a (xen-netback: fix > unlimited guest Rx internal queue and carrier flapping) introduced a > regression. > > The PV frontend in IPXE only places 4 requests on the guest Rx ring. > Since netback required at least (MAX_SKB_FRAGS + 1) slots, IPXE could > not receive any packets. > > a) If GSO is not enabled on the VIF, fewer guest Rx slots are required > for the largest possible packet. Calculate the required slots > based on the maximum GSO size or the MTU. > > This calculation of the number of required slots relies on > 1650d5455bd2 (xen-netback: always fully coalesce guest Rx packets) > which present in 4.0-rc1 and later. > > b) Reduce the Rx stall detection to checking for at least one > available Rx request. This is fine since we're predominately > concerned with detecting interfaces which are down and thus have > zero available Rx requests. > > Signed-off-by: David Vrabel <david.vrabel@...rix.com> Applied, thanks David. -- 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
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