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Date: Thu, 15 May 2014 15:13:22 +0100
From: Wei Liu <wei.liu2@...rix.com>
To: Jacek Konieczny <jajcus@...cus.net>
CC: Wei Liu <wei.liu2@...rix.com>, <xen-devel@...ts.xen.org>,
<netdev@...r.kernel.org>, Paul Durrant <paul.durrant@...rix.com>
Subject: Re: [PATCH net V2] xen-netback: don't move event pointer in TX
credit timeout callback
On Thu, May 15, 2014 at 03:04:36PM +0200, Jacek Konieczny wrote:
> On 05/15/14 13:59, Wei Liu wrote:
> > ... otherwise the frontend will try to send TX event all the time, even
> > if no progress can be made. The pointer should only be advanced by the
> > routine that actually processes the ring (that is, xenvif_poll).
> >
> > Reported-by: Jacek Konieczny <jajcus@...cus.net>
> > Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> > Acked-by: Ian Campbell <ian.campbell@...rix.com>
> > Cc: Paul Durrant <paul.durrant@...rix.com>
> > ---
> > drivers/net/xen-netback/netback.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> > index 7666540..8e2cbeb 100644
> > --- a/drivers/net/xen-netback/netback.c
> > +++ b/drivers/net/xen-netback/netback.c
> > @@ -658,7 +658,7 @@ void xenvif_check_rx_xenvif(struct xenvif *vif)
> > {
> > int more_to_do;
> >
> > - RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do);
> > + more_to_do = RING_HAS_UNCONSUMED_REQUESTS(&vif->tx);
> >
>
> Unfortunately, this seems not enough to fix the problem I have reported
> here:
> http://lists.xenproject.org/archives/html/xen-devel/2014-05/msg01183.html
>
> The dom0 network still stalls when using rate limiting on a VIF
> interface after applying this patch to my 3.14.3 kernel (100% CPU#1
> usage in the 'soft interrupts').
>
This is a patch for 3.14.4. I've tested it myself (and looking at the
right stats!) to confirm it works.
---8<---
>From a4afed6c44027afff82d6fa7503faef83b01fffe Mon Sep 17 00:00:00 2001
From: Wei Liu <wei.liu2@...rix.com>
Date: Thu, 15 May 2014 15:02:55 +0100
Subject: [PATCH] xen-netback: call napi_complete if vif is rate limited
Reported-by: Jacek Konieczny <jajcus@...cus.net>
Signed-off-by: Wei Liu <wei.liu2@...rix.com>
Cc: Ian Campbell <ian.campbell@...rix.com>
Cc: Paul Durrant <paul.durrant@...rix.com>
Cc: David Vrabel <david.vrabel@...rix.com>
---
drivers/net/xen-netback/common.h | 2 +-
drivers/net/xen-netback/interface.c | 5 +++--
drivers/net/xen-netback/netback.c | 12 ++++++++----
3 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 4bf5b33..4c018de 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -219,7 +219,7 @@ void xenvif_check_rx_xenvif(struct xenvif *vif);
/* Prevent the device from generating any further traffic. */
void xenvif_carrier_off(struct xenvif *vif);
-int xenvif_tx_action(struct xenvif *vif, int budget);
+int xenvif_tx_action(struct xenvif *vif, int budget, bool *rate_limited);
int xenvif_kthread(void *data);
void xenvif_kick_thread(struct xenvif *vif);
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 2e92d52..03cfbd6 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -61,6 +61,7 @@ static int xenvif_poll(struct napi_struct *napi, int budget)
{
struct xenvif *vif = container_of(napi, struct xenvif, napi);
int work_done;
+ bool rate_limited;
/* This vif is rogue, we pretend we've there is nothing to do
* for this vif to deschedule it from NAPI. But this interface
@@ -71,7 +72,7 @@ static int xenvif_poll(struct napi_struct *napi, int budget)
return 0;
}
- work_done = xenvif_tx_action(vif, budget);
+ work_done = xenvif_tx_action(vif, budget, &rate_limited);
if (work_done < budget) {
int more_to_do = 0;
@@ -96,7 +97,7 @@ static int xenvif_poll(struct napi_struct *napi, int budget)
local_irq_save(flags);
RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do);
- if (!more_to_do)
+ if (!more_to_do || rate_limited)
__napi_complete(napi);
local_irq_restore(flags);
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 97030c1..fa7d5da 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1125,12 +1125,14 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
return false;
}
-static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
+static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget,
+ bool *rate_limited)
{
struct gnttab_copy *gop = vif->tx_copy_ops, *request_gop;
struct sk_buff *skb;
int ret;
+ *rate_limited = false;
while ((nr_pending_reqs(vif) + XEN_NETBK_LEGACY_SLOTS_MAX
< MAX_PENDING_REQS) &&
(skb_queue_len(&vif->tx_queue) < budget)) {
@@ -1165,8 +1167,10 @@ static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
/* Credit-based scheduling. */
if (txreq.size > vif->remaining_credit &&
- tx_credit_exceeded(vif, txreq.size))
+ tx_credit_exceeded(vif, txreq.size)) {
+ *rate_limited = true;
break;
+ }
vif->remaining_credit -= txreq.size;
@@ -1382,7 +1386,7 @@ static int xenvif_tx_submit(struct xenvif *vif)
}
/* Called after netfront has transmitted */
-int xenvif_tx_action(struct xenvif *vif, int budget)
+int xenvif_tx_action(struct xenvif *vif, int budget, bool *rate_limited)
{
unsigned nr_gops;
int work_done;
@@ -1390,7 +1394,7 @@ int xenvif_tx_action(struct xenvif *vif, int budget)
if (unlikely(!tx_work_todo(vif)))
return 0;
- nr_gops = xenvif_tx_build_gops(vif, budget);
+ nr_gops = xenvif_tx_build_gops(vif, budget, rate_limited);
if (nr_gops == 0)
return 0;
--
1.7.10.4
> Greets,
> Jacek
--
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