| Message ID | 20240402145305.82148-1-paul.barker.ct@bp.renesas.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 596a4254915f94c927217fe09c33a6828f33fb25 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2,1/2] net: ravb: Always process TX descriptor ring | expand |
On 4/2/24 5:53 PM, Paul Barker wrote: > The TX queue should be serviced each time the poll function is called, > even if the full RX work budget has been consumed. This prevents > starvation of the TX queue when RX bandwidth usage is high. > > Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper") > Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com> Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru> [...] MBR, Sergey
On 2024-04-02 at 20:23:04, Paul Barker (paul.barker.ct@bp.renesas.com) wrote: > The TX queue should be serviced each time the poll function is called, > even if the full RX work budget has been consumed. This prevents > starvation of the TX queue when RX bandwidth usage is high. > > Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper") > Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com> > --- > Changes from v1: > * Use the correct 'Fixes' tag. > * Call the new variable 'unmask' and drop the unnecessary initializer, > as requested by Sergey. > > drivers/net/ethernet/renesas/ravb_main.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c > index d1be030c8848..48803050abdb 100644 > --- a/drivers/net/ethernet/renesas/ravb_main.c > +++ b/drivers/net/ethernet/renesas/ravb_main.c > @@ -1324,12 +1324,12 @@ static int ravb_poll(struct napi_struct *napi, int budget) > int q = napi - priv->napi; > int mask = BIT(q); > int quota = budget; > + bool unmask; > > /* Processing RX Descriptor Ring */ > /* Clear RX interrupt */ > ravb_write(ndev, ~(mask | RIS0_RESERVED), RIS0); > - if (ravb_rx(ndev, "a, q)) > - goto out; > + unmask = !ravb_rx(ndev, "a, q); > > /* Processing TX Descriptor Ring */ AFAIU, TX is processed without any budget. This wont result in rx work starvation if TX traffic is more ? > spin_lock_irqsave(&priv->lock, flags); > @@ -1339,6 +1339,9 @@ static int ravb_poll(struct napi_struct *napi, int budget) > netif_wake_subqueue(ndev, q); > spin_unlock_irqrestore(&priv->lock, flags); > > + if (!unmask) > + goto out; > + > napi_complete(napi); > > /* Re-enable RX/TX interrupts */ > > base-commit: ea2a1cfc3b2019bdea6324acd3c03606b60d71ad > -- > 2.39.2 >
On 03/04/2024 04:39, Ratheesh Kannoth wrote: > On 2024-04-02 at 20:23:04, Paul Barker (paul.barker.ct@bp.renesas.com) wrote: >> The TX queue should be serviced each time the poll function is called, >> even if the full RX work budget has been consumed. This prevents >> starvation of the TX queue when RX bandwidth usage is high. >> >> Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper") >> Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com> >> --- >> Changes from v1: >> * Use the correct 'Fixes' tag. >> * Call the new variable 'unmask' and drop the unnecessary initializer, >> as requested by Sergey. >> >> drivers/net/ethernet/renesas/ravb_main.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c >> index d1be030c8848..48803050abdb 100644 >> --- a/drivers/net/ethernet/renesas/ravb_main.c >> +++ b/drivers/net/ethernet/renesas/ravb_main.c >> @@ -1324,12 +1324,12 @@ static int ravb_poll(struct napi_struct *napi, int budget) >> int q = napi - priv->napi; >> int mask = BIT(q); >> int quota = budget; >> + bool unmask; >> >> /* Processing RX Descriptor Ring */ >> /* Clear RX interrupt */ >> ravb_write(ndev, ~(mask | RIS0_RESERVED), RIS0); >> - if (ravb_rx(ndev, "a, q)) >> - goto out; >> + unmask = !ravb_rx(ndev, "a, q); >> >> /* Processing TX Descriptor Ring */ > AFAIU, TX is processed without any budget. This wont result in rx work starvation if > TX traffic is more ? Quoting the docs in Documentation/networking/napi.rst: The method takes a ``budget`` argument - drivers can process completions for any number of Tx packets but should only process up to ``budget`` number of Rx packets. skb Tx processing should happen regardless of the ``budget`` I take that to mean that the RX work budget running out should not stop processing of TX packets. Other drivers with a combined TX/RX poll function follow the same pattern of processing TX packets regardless of RX budget exhaustion, for example see ixgbe_poll() which processes TX packets first (in drivers/net/ethernet/intel/ixgbe/ixgbe_main.c). Thanks,
> From: Paul Barker <paul.barker.ct@bp.renesas.com> > > AFAIU, TX is processed without any budget. This wont result in rx work > > starvation if TX traffic is more ? > > Quoting the docs in Documentation/networking/napi.rst: > > The method takes a ``budget`` argument - drivers can process > completions for any number of Tx packets but should only process up > to ``budget`` number of Rx packets. > > skb Tx processing should happen regardless of the ``budget`` > > I take that to mean that the RX work budget running out should not stop > processing of TX packets. > > Other drivers with a combined TX/RX poll function follow the same pattern of > processing TX packets regardless of RX budget exhaustion, for example see > ixgbe_poll() which processes TX packets first (in > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c). ACK. Thanks for pointing out. I had seen some drivers, TX NAPI routines exist to bring fairness to rx and tx. Just wondering, if there is a lot of tx traffic, would RX budget alone can do fairness among NAPI Routines.
Hello: This series was applied to netdev/net.git (main) by Paolo Abeni <pabeni@redhat.com>: On Tue, 2 Apr 2024 15:53:04 +0100 you wrote: > The TX queue should be serviced each time the poll function is called, > even if the full RX work budget has been consumed. This prevents > starvation of the TX queue when RX bandwidth usage is high. > > Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper") > Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com> > > [...] Here is the summary with links: - [v2,1/2] net: ravb: Always process TX descriptor ring https://git.kernel.org/netdev/net/c/596a4254915f - [v2,2/2] net: ravb: Always update error counters https://git.kernel.org/netdev/net/c/101b76418d71 You are awesome, thank you!
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c index d1be030c8848..48803050abdb 100644 --- a/drivers/net/ethernet/renesas/ravb_main.c +++ b/drivers/net/ethernet/renesas/ravb_main.c @@ -1324,12 +1324,12 @@ static int ravb_poll(struct napi_struct *napi, int budget) int q = napi - priv->napi; int mask = BIT(q); int quota = budget; + bool unmask; /* Processing RX Descriptor Ring */ /* Clear RX interrupt */ ravb_write(ndev, ~(mask | RIS0_RESERVED), RIS0); - if (ravb_rx(ndev, "a, q)) - goto out; + unmask = !ravb_rx(ndev, "a, q); /* Processing TX Descriptor Ring */ spin_lock_irqsave(&priv->lock, flags); @@ -1339,6 +1339,9 @@ static int ravb_poll(struct napi_struct *napi, int budget) netif_wake_subqueue(ndev, q); spin_unlock_irqrestore(&priv->lock, flags); + if (!unmask) + goto out; + napi_complete(napi); /* Re-enable RX/TX interrupts */
The TX queue should be serviced each time the poll function is called, even if the full RX work budget has been consumed. This prevents starvation of the TX queue when RX bandwidth usage is high. Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper") Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com> --- Changes from v1: * Use the correct 'Fixes' tag. * Call the new variable 'unmask' and drop the unnecessary initializer, as requested by Sergey. drivers/net/ethernet/renesas/ravb_main.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) base-commit: ea2a1cfc3b2019bdea6324acd3c03606b60d71ad