[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH V6 net-next 1/5] xen-netback: Factor queue-specific data into queue struct.
On 14/03/14 15:55, Ian Campbell wrote: On Mon, 2014-03-03 at 11:47 +0000, Andrew J. Bennieston wrote:From: "Andrew J. Bennieston" <andrew.bennieston@xxxxxxxxxx> In preparation for multi-queue support in xen-netback, move the queue-specific data from struct xenvif into struct xenvif_queue, and update the rest of the code to use this. Also[...] Finally,[...]This is already quite a big patch, and I don't think the commit log covers everything it changes/refactors, does it? It's always a good idea to break these things apart but in particular separating the mechanical stuff (s/vif/queue/g) from the non-mechanical stuff, since the mechanical stuff is essentially trivial to review and getting it out the way makes the non-mechanical stuff much easier to check (or even spot). The vast majority of changes in this patch are s/vif/queue/g. The rest are related changes, such as inserting loops over queues, and moving queue-specific initialisation away from the vif-wide initialisation, so that it can be done once per queue. I consider these things to be logically related and definitely within the purview of this single patch. Without doing this, it is difficult to get a patch that results in something that even compiles, without putting in a bunch of placeholder code that will be removed in the very next patch. When I split this feature into multiple patches, I took care to group as little as possible into this first patch (and the same for netfront). It is still a large patch, but by my count most of this is a simple replacement of vif with queue... A first-order approximation, searching for line pairs where the first has 'vif' and the second has 'queue', yields:â xen-netback git:(saturn) git show HEAD~4 | grep -A 1 vif | grep queue | wc -l 380 i.e. 760 (=380*2) lines out of the 2240 (~ 40%) are trivial replacements of vif with queue, and this is not counting multi-line replacements, of which there are many. What remains is mostly adding loops over these queues. This could, in principle, be done in a second patch, but the impact of this is small. Signed-off-by: Andrew J. Bennieston <andrew.bennieston@xxxxxxxxxx> Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx> --- drivers/net/xen-netback/common.h | 85 ++++-- drivers/net/xen-netback/interface.c | 329 ++++++++++++++-------- drivers/net/xen-netback/netback.c | 530 ++++++++++++++++++----------------- drivers/net/xen-netback/xenbus.c | 87 ++++-- 4 files changed, 608 insertions(+), 423 deletions(-) diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h index ae413a2..4176539 100644 --- a/drivers/net/xen-netback/common.h +++ b/drivers/net/xen-netback/common.h @@ -108,17 +108,39 @@ struct xenvif_rx_meta { */ #define MAX_GRANT_COPY_OPS (MAX_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE) -struct xenvif { - /* Unique identifier for this interface. */ - domid_t domid; - unsigned int handle; +/* Queue name is interface name with "-qNNN" appended */ +#define QUEUE_NAME_SIZE (IFNAMSIZ + 6)One more than necessary? Or does IFNAMSIZ not include the NULL? (I can't figure out if it does or not!) interface.c contains the line: snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle); This suggests that IFNAMSIZ counts the trailing NULL, so I can reduce this count by 1 on that basis. [...] - /* This array is allocated seperately as it is large */ - struct gnttab_copy *grant_copy_op; + struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];Is this deliberate? It seems like a retrograde step reverting parts of ac3d5ac27735 "xen-netback: fix guest-receive-side array sizes" from Paul (at least you are nuking a speeling erorr) Yes, this was deliberate. These arrays were moved out to avoid problems with kmalloc for the struct net_device (which contains the struct xenvif in its netdev_priv space). Since the queues are now allocated via vzalloc, there is no need to do separate allocations (with the requirement to also separately free on every error/teardown path) so I moved these back into the main queue structure. How does this series interact with Zoltan's foreign mapping one? Badly I should imagine, are you going to rebase? I'm working on the rebase right now. + /* First, check if there is only one queue to optimise the + * single-queue or old frontend scenario. + */ + if (vif->num_queues == 1) { + queue_index = 0; + } else { + /* Use skb_get_hash to obtain an L4 hash if available */ + hash = skb_get_hash(skb); + queue_index = (u16) (((u64)hash * vif->num_queues) >> 32);No modulo num_queues here? Is the multiply and shift from some best practice somewhere? Or else what is it doing? It seems to be what a bunch of other net drivers do in this scenario. I guess the reasoning is it'll be faster than a mod num_queues. + /* Obtain the queue to be used to transmit this packet */ + index = skb_get_queue_mapping(skb); + if (index >= vif->num_queues) + index = 0; /* Fall back to queue 0 if out of range */Is this actually allowed to happen? Even if yes, not modulo num_queue so spread it around a bit? This probably isn't allowed to happen. I figured it didn't hurt to be a little defensive with the code here, and falling back to queue 0 is a fairly safe thing to do. static void xenvif_up(struct xenvif *vif) { - napi_enable(&vif->napi); - enable_irq(vif->tx_irq); - if (vif->tx_irq != vif->rx_irq) - enable_irq(vif->rx_irq); - xenvif_check_rx_xenvif(vif); + struct xenvif_queue *queue = NULL; + unsigned int queue_index; + + for (queue_index = 0; queue_index < vif->num_queues; ++queue_index) {This vif->num_queues -- is it the same as dev->num_tx_queues? Or areew there differing concepts of queue around? It should be the same as dev->real_num_tx_queues, which may be less than dev->num_tx_queues. + queue = &vif->queues[queue_index]; + napi_enable(&queue->napi); + enable_irq(queue->tx_irq); + if (queue->tx_irq != queue->rx_irq) + enable_irq(queue->rx_irq); + xenvif_check_rx_xenvif(queue); + } } static void xenvif_down(struct xenvif *vif) { - napi_disable(&vif->napi); - disable_irq(vif->tx_irq); - if (vif->tx_irq != vif->rx_irq) - disable_irq(vif->rx_irq); - del_timer_sync(&vif->credit_timeout); + struct xenvif_queue *queue = NULL; + unsigned int queue_index;Why unsigned? Why not? You can't have a negative number of queues. Zero indicates "I don't have any set up yet". I'm not expecting people to have 4 billion or so queues, but equally I can't see a valid use for negative values here. @@ -496,9 +497,30 @@ static void connect(struct backend_info *be) return; } - xen_net_read_rate(dev, &be->vif->credit_bytes, - &be->vif->credit_usec); - be->vif->remaining_credit = be->vif->credit_bytes; + xen_net_read_rate(dev, &credit_bytes, &credit_usec); + read_xenbus_vif_flags(be); + + be->vif->num_queues = 1; + be->vif->queues = vzalloc(be->vif->num_queues * + sizeof(struct xenvif_queue)); + + for (queue_index = 0; queue_index < be->vif->num_queues; ++queue_index) { + queue = &be->vif->queues[queue_index]; + queue->vif = be->vif; + queue->id = queue_index; + snprintf(queue->name, sizeof(queue->name), "%s-q%u", + be->vif->dev->name, queue->id); + + xenvif_init_queue(queue); + + queue->remaining_credit = credit_bytes; + + err = connect_rings(be, queue); + if (err) + goto err; + } + + xenvif_carrier_on(be->vif); unregister_hotplug_status_watch(be); err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch, @@ -507,18 +529,24 @@ static void connect(struct backend_info *be) if (!err) be->have_hotplug_status_watch = 1; - netif_wake_queue(be->vif->dev); + netif_tx_wake_all_queues(be->vif->dev); + + return; + +err: + vfree(be->vif->queues); + be->vif->queues = NULL; + be->vif->num_queues = 0; + return;Do you not need to unwind the setup already done on the previous queues before the failure? Err... yes. I was sure that code existed at some point, but I can't find it now. Oops! -Andrew } -static int connect_rings(struct backend_info *be) +static int connect_rings(struct backend_info *be, struct xenvif_queue *queue) { - struct xenvif *vif = be->vif; struct xenbus_device *dev = be->dev; unsigned long tx_ring_ref, rx_ring_ref; - unsigned int tx_evtchn, rx_evtchn, rx_copy; + unsigned int tx_evtchn, rx_evtchn; int err; - int val; err = xenbus_gather(XBT_NIL, dev->otherend, "tx-ring-ref", "%lu", &tx_ring_ref, @@ -546,6 +574,27 @@ static int connect_rings(struct backend_info *be) rx_evtchn = tx_evtchn; } + /* Map the shared frame, irq etc. */ + err = xenvif_connect(queue, tx_ring_ref, rx_ring_ref, + tx_evtchn, rx_evtchn); + if (err) { + xenbus_dev_fatal(dev, err, + "mapping shared-frames %lu/%lu port tx %u rx %u", + tx_ring_ref, rx_ring_ref, + tx_evtchn, rx_evtchn); + return err; + } + + return 0; +} + _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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