[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH V3] netif.h: Document xen-net{back, front} multi-queue feature
From: "Andrew J. Bennieston" <andrew.bennieston@xxxxxxxxxx> Document the multi-queue feature in terms of XenStore keys to be written by the backend and by the frontend. Signed-off-by: Andrew J. Bennieston <andrew.bennieston@xxxxxxxxxx> --- Changes since V2: - Clarified several areas of text which may be confusing or ambiguous. - Made clear that split event channels may be used in conjunction with multiple queues, but are not required. --- xen/include/public/io/netif.h | 46 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h index d7fb771..0c3b5bd 100644 --- a/xen/include/public/io/netif.h +++ b/xen/include/public/io/netif.h @@ -69,6 +69,52 @@ */ /* + * Multiple transmit and receive queues: + * If supported, the backend will write the key "multi-queue-max-queues" to + * the directory for that vif, and set its value to the maximum supported + * number of queues. + * Frontends that are aware of this feature and wish to use it can write the + * key "multi-queue-num-queues", set to the number they wish to use. + * + * Queues replicate the shared rings and event channels, and + * "feature-split-event-channels" may be used when using multiple queues, but + * are not required to do so. + * + * Each queue consists of one shared ring pair, i.e. there must be the same + * number of tx and rx rings. + * + * For frontends requesting just one queue, the usual event-channel and + * ring-ref keys are written as before, simplifying the backend processing + * to avoid distinguishing between a frontend that doesn't understand the + * multi-queue feature, and one that does, but requested only one queue. + * + * Frontends requesting two or more queues must not write the toplevel + * event-channel (or event-channel-{tx,rx}) and {tx,rx}-ring-ref keys, + * instead writing those keys under sub-keys having the name "queue-N" where + * N is the integer ID of the queue for which those keys belong. Queues + * are indexed from zero. For example, a frontend with two queues and split + * event channels may write the following set of queue-related keys: + * + * /local/domain/1/device/vif/0/multi-queue-num-queues = "2" + * /local/domain/1/device/vif/0/queue-0 = "" + * /local/domain/1/device/vif/0/queue-0/tx-ring-ref = "<ring-ref-tx0>" + * /local/domain/1/device/vif/0/queue-0/rx-ring-ref = "<ring-ref-rx0>" + * /local/domain/1/device/vif/0/queue-0/event-channel-tx = "<evtchn-tx0>" + * /local/domain/1/device/vif/0/queue-0/event-channel-rx = "<evtchn-rx0>" + * /local/domain/1/device/vif/0/queue-1 = "" + * /local/domain/1/device/vif/0/queue-1/tx-ring-ref = "<ring-ref-tx1>" + * /local/domain/1/device/vif/0/queue-1/rx-ring-ref = "<ring-ref-rx1" + * /local/domain/1/device/vif/0/queue-1/event-channel-tx = "<evtchn-tx1>" + * /local/domain/1/device/vif/0/queue-1/event-channel-rx = "<evtchn-rx1>" + * + * Mapping of packets to queues is considered to be a function of the + * transmitting system (backend or frontend) and is not negotiated + * between the two. Guests are free to transmit packets on any queue + * they choose, provided it has been set up correctly. Guests must be + * prepared to receive packets on any queue they have requested be set up. + */ + +/* * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP checksum * offload off or on. If it is missing then the feature is assumed to be on. * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP checksum -- 1.7.10.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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