Wei Liu
2013-Oct-08 09:54 UTC
[PATCH net-next] Revert "xen-netback: improve ring effeciency for guest RX"
This reverts commit 4f0581d25827d5e864bcf07b05d73d0d12a20a5c.
The named changeset is causing problem. Let''s aim to make this part
less
fragile before trying to improve things.
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Annie Li <annie.li@oracle.com>
Cc: Matt Wilson <msw@amazon.com>
Cc: Xi Xiong <xixiong@amazon.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Paul Durrant <paul.durrant@citrix.com>
---
drivers/net/xen-netback/netback.c | 144 +++++++++++++++++++++----------------
1 file changed, 83 insertions(+), 61 deletions(-)
diff --git a/drivers/net/xen-netback/netback.c
b/drivers/net/xen-netback/netback.c
index d0b0feb..f3e591c 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -47,14 +47,6 @@
#include <asm/xen/hypercall.h>
#include <asm/xen/page.h>
-/* SKB control block overlay is used to store useful information when
- * doing guest RX.
- */
-struct skb_cb_overlay {
- int meta_slots_used;
- int peek_slots_count;
-};
-
/* Provide an option to disable split event channels at load time as
* event channels are limited resource. Split event channels are
* enabled by default.
@@ -220,6 +212,49 @@ static bool start_new_rx_buffer(int offset, unsigned long
size, int head)
return false;
}
+struct xenvif_count_slot_state {
+ unsigned long copy_off;
+ bool head;
+};
+
+unsigned int xenvif_count_frag_slots(struct xenvif *vif,
+ unsigned long offset, unsigned long size,
+ struct xenvif_count_slot_state *state)
+{
+ unsigned count = 0;
+
+ offset &= ~PAGE_MASK;
+
+ while (size > 0) {
+ unsigned long bytes;
+
+ bytes = PAGE_SIZE - offset;
+
+ if (bytes > size)
+ bytes = size;
+
+ if (start_new_rx_buffer(state->copy_off, bytes, state->head)) {
+ count++;
+ state->copy_off = 0;
+ }
+
+ if (state->copy_off + bytes > MAX_BUFFER_OFFSET)
+ bytes = MAX_BUFFER_OFFSET - state->copy_off;
+
+ state->copy_off += bytes;
+
+ offset += bytes;
+ size -= bytes;
+
+ if (offset == PAGE_SIZE)
+ offset = 0;
+
+ state->head = false;
+ }
+
+ return count;
+}
+
/*
* Figure out how many ring slots we''re going to need to send @skb to
* the guest. This function is essentially a dry run of
@@ -227,53 +262,40 @@ static bool start_new_rx_buffer(int offset, unsigned long
size, int head)
*/
unsigned int xenvif_count_skb_slots(struct xenvif *vif, struct sk_buff *skb)
{
+ struct xenvif_count_slot_state state;
unsigned int count;
- int i, copy_off;
- struct skb_cb_overlay *sco;
+ unsigned char *data;
+ unsigned i;
- count = DIV_ROUND_UP(skb_headlen(skb), PAGE_SIZE);
+ state.head = true;
+ state.copy_off = 0;
- copy_off = skb_headlen(skb) % PAGE_SIZE;
+ /* Slot for the first (partial) page of data. */
+ count = 1;
+ /* Need a slot for the GSO prefix for GSO extra data? */
if (skb_shinfo(skb)->gso_size)
count++;
- for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
- unsigned long size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
- unsigned long offset = skb_shinfo(skb)->frags[i].page_offset;
- unsigned long bytes;
-
- offset &= ~PAGE_MASK;
-
- while (size > 0) {
- BUG_ON(offset >= PAGE_SIZE);
- BUG_ON(copy_off > MAX_BUFFER_OFFSET);
-
- bytes = PAGE_SIZE - offset;
-
- if (bytes > size)
- bytes = size;
+ data = skb->data;
+ while (data < skb_tail_pointer(skb)) {
+ unsigned long offset = offset_in_page(data);
+ unsigned long size = PAGE_SIZE - offset;
- if (start_new_rx_buffer(copy_off, bytes, 0)) {
- count++;
- copy_off = 0;
- }
+ if (data + size > skb_tail_pointer(skb))
+ size = skb_tail_pointer(skb) - data;
- if (copy_off + bytes > MAX_BUFFER_OFFSET)
- bytes = MAX_BUFFER_OFFSET - copy_off;
+ count += xenvif_count_frag_slots(vif, offset, size, &state);
- copy_off += bytes;
+ data += size;
+ }
- offset += bytes;
- size -= bytes;
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+ unsigned long size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
+ unsigned long offset = skb_shinfo(skb)->frags[i].page_offset;
- if (offset == PAGE_SIZE)
- offset = 0;
- }
+ count += xenvif_count_frag_slots(vif, offset, size, &state);
}
-
- sco = (struct skb_cb_overlay *)skb->cb;
- sco->peek_slots_count = count;
return count;
}
@@ -305,11 +327,14 @@ static struct xenvif_rx_meta *get_next_rx_buffer(struct
xenvif *vif,
return meta;
}
-/* Set up the grant operations for this fragment. */
+/*
+ * Set up the grant operations for this fragment. If it''s a flipping
+ * interface, we also set up the unmap request from here.
+ */
static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
struct netrx_pending_operations *npo,
struct page *page, unsigned long size,
- unsigned long offset, int head, int *first)
+ unsigned long offset, int *head)
{
struct gnttab_copy *copy_gop;
struct xenvif_rx_meta *meta;
@@ -333,12 +358,12 @@ static void xenvif_gop_frag_copy(struct xenvif *vif,
struct sk_buff *skb,
if (bytes > size)
bytes = size;
- if (start_new_rx_buffer(npo->copy_off, bytes, head)) {
+ if (start_new_rx_buffer(npo->copy_off, bytes, *head)) {
/*
* Netfront requires there to be some data in the head
* buffer.
*/
- BUG_ON(*first);
+ BUG_ON(*head);
meta = get_next_rx_buffer(vif, npo);
}
@@ -372,10 +397,10 @@ static void xenvif_gop_frag_copy(struct xenvif *vif,
struct sk_buff *skb,
}
/* Leave a gap for the GSO descriptor. */
- if (*first && skb_shinfo(skb)->gso_size &&
!vif->gso_prefix)
+ if (*head && skb_shinfo(skb)->gso_size &&
!vif->gso_prefix)
vif->rx.req_cons++;
- *first = 0; /* There must be something in this buffer now. */
+ *head = 0; /* There must be something in this buffer now. */
}
}
@@ -401,7 +426,7 @@ static int xenvif_gop_skb(struct sk_buff *skb,
struct xen_netif_rx_request *req;
struct xenvif_rx_meta *meta;
unsigned char *data;
- int first = 1;
+ int head = 1;
int old_meta_prod;
old_meta_prod = npo->meta_prod;
@@ -437,7 +462,7 @@ static int xenvif_gop_skb(struct sk_buff *skb,
len = skb_tail_pointer(skb) - data;
xenvif_gop_frag_copy(vif, skb, npo,
- virt_to_page(data), len, offset, 1, &first);
+ virt_to_page(data), len, offset, &head);
data += len;
}
@@ -446,7 +471,7 @@ static int xenvif_gop_skb(struct sk_buff *skb,
skb_frag_page(&skb_shinfo(skb)->frags[i]),
skb_frag_size(&skb_shinfo(skb)->frags[i]),
skb_shinfo(skb)->frags[i].page_offset,
- 0, &first);
+ &head);
}
return npo->meta_prod - old_meta_prod;
@@ -504,6 +529,10 @@ static void xenvif_add_frag_responses(struct xenvif *vif,
int status,
}
}
+struct skb_cb_overlay {
+ int meta_slots_used;
+};
+
static void xenvif_kick_thread(struct xenvif *vif)
{
wake_up(&vif->wq);
@@ -534,26 +563,19 @@ void xenvif_rx_action(struct xenvif *vif)
count = 0;
while ((skb = skb_dequeue(&vif->rx_queue)) != NULL) {
- RING_IDX old_rx_req_cons;
-
vif = netdev_priv(skb->dev);
nr_frags = skb_shinfo(skb)->nr_frags;
- old_rx_req_cons = vif->rx.req_cons;
sco = (struct skb_cb_overlay *)skb->cb;
sco->meta_slots_used = xenvif_gop_skb(skb, &npo);
- count += vif->rx.req_cons - old_rx_req_cons;
+ count += nr_frags + 1;
__skb_queue_tail(&rxq, skb);
- skb = skb_peek(&vif->rx_queue);
- if (skb == NULL)
- break;
- sco = (struct skb_cb_overlay *)skb->cb;
-
/* Filled the batch queue? */
- if (count + sco->peek_slots_count >= XEN_NETIF_RX_RING_SIZE)
+ /* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */
+ if (count + MAX_SKB_FRAGS >= XEN_NETIF_RX_RING_SIZE)
break;
}
--
1.7.10.4
Ian Campbell
2013-Oct-08 10:21 UTC
Re: [PATCH net-next] Revert "xen-netback: improve ring effeciency for guest RX"
On Tue, 2013-10-08 at 10:54 +0100, Wei Liu wrote:> This reverts commit 4f0581d25827d5e864bcf07b05d73d0d12a20a5c. > > The named changeset is causing problem. Let''s aim to make this part less > fragile before trying to improve things. > > Signed-off-by: Wei Liu <wei.liu2@citrix.com>Acked-by: Ian Campbell <ian.campbell@citrix.com> Although I thought davem would just run git revert so I don''t know if it is needed.
David Miller
2013-Oct-08 19:11 UTC
Re: [PATCH net-next] Revert "xen-netback: improve ring effeciency for guest RX"
From: Ian Campbell <ian.campbell@citrix.com> Date: Tue, 8 Oct 2013 11:21:47 +0100> On Tue, 2013-10-08 at 10:54 +0100, Wei Liu wrote: >> This reverts commit 4f0581d25827d5e864bcf07b05d73d0d12a20a5c. >> >> The named changeset is causing problem. Let''s aim to make this part less >> fragile before trying to improve things. >> >> Signed-off-by: Wei Liu <wei.liu2@citrix.com> > Acked-by: Ian Campbell <ian.campbell@citrix.com> > > Although I thought davem would just run git revert so I don''t know if it > is needed.This works too, because it gives you guys an opportunity to add some explanation to the commit message. Applied, thanks.