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Re: [Xen-devel] [PATCH 6/8] netfront: multi-page ring support
On 2013-2-26 20:35, Wei Liu wrote:
On Tue, 2013-02-26 at 06:52 +0000, ANNIE LI wrote:
On 2013-2-16 0:00, Wei Liu wrote:
Signed-off-by: Wei Liu<wei.liu2@xxxxxxxxxx>
---
drivers/net/xen-netfront.c | 246
+++++++++++++++++++++++++++++++-------------
1 file changed, 174 insertions(+), 72 deletions(-)
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 8bd75a1..de73a71 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -67,9 +67,19 @@ struct netfront_cb {
#define GRANT_INVALID_REF 0
-#define NET_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
-#define NET_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)
-#define TX_MAX_TARGET min_t(int, NET_TX_RING_SIZE, 256)
+#define XENNET_MAX_RING_PAGE_ORDER XENBUS_MAX_RING_PAGE_ORDER
+#define XENNET_MAX_RING_PAGES (1U<< XENNET_MAX_RING_PAGE_ORDER)
+
+
+#define NET_TX_RING_SIZE(_nr_pages) \
+ __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE * (_nr_pages))
+#define NET_RX_RING_SIZE(_nr_pages) \
+ __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE * (_nr_pages))
+
+#define XENNET_MAX_TX_RING_SIZE NET_TX_RING_SIZE(XENNET_MAX_RING_PAGES)
+#define XENNET_MAX_RX_RING_SIZE NET_RX_RING_SIZE(XENNET_MAX_RING_PAGES)
+
+#define TX_MAX_TARGET min_t(int, NET_TX_RING_SIZE(1), 256)
Not using multi-page ring here?
In xennet_create_dev, gnttab_alloc_grant_references allocates
TX_MAX_TARGET number of grant reference for tx. In
xennet_release_tx_bufs, NET_TX_RING_SIZE(np->tx_ring_pages) numbers of
grants are processed. And NET_RX_RING_SIZE(np->tx_ring_pages) is totally
different from TX_MAX_TARGET if np->rx_ring_pages is not 1. Although
skb_entry_is_link helps to not release invalid grants, lots of null loop
seems unnecessary. I think TX_MAX_TARGET should be changed into some
variableconnected with np->tx_ring_pages. Or you intended to use one
page ring here?
Looking back my history, this limitation was introduced because if we
have a multi-page backend and single page frontend, the backend skb
processing could overlap.
I did not see the overlap you mentioned here in netback. Although
netback supports multi-page, netback->vif still uses single page if the
frontend only supports single page. Netfront and netback negotiate this
through xenstore in your 5/8 patch. The requests and response should not
have any overlap between netback and netfront. Am I missing something?
I agree with you that this limit should be variable, but as we still use
M:N model, the safe option is to cap this limit to 1 page.
Yes, M:N model is still used here. But the share ring should be same for
netback->vif and netfront.
Thanks
Annie
Another option is to check validity of skbs before processing them. I
will look into that as well.
The same reason applies to the RX ring as well.
Wei.
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