Re: [RFC net-next 05/14] Fix intel/ixgbevf

On Tue, 19 Jun 2012 19:06:53 +0300
Eilon Greenstein [off-list ref] wrote:

On Tue, 2012-06-19 at 08:39 -0700, Alexander Duyck wrote:

quoted

On 06/19/2012 08:13 AM, Yuval Mintz wrote:

quoted

Signed-off-by: Yuval Mintz <redacted>
Signed-off-by: Eilon Greenstein <redacted>

Cc: Jeff Kirsher <redacted>
---
 drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c

b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c index
f69ec42..3ad46c2 100644 ---
a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c +++
b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c @@ -2014,7
+2014,7 @@ err_tx_ring_allocation: static int
ixgbevf_set_interrupt_capability(struct ixgbevf_adapter *adapter)
{ int err = 0;
-	int vector, v_budget;
+	int vector, v_budget, ncpu;
 
 	/*
 	 * It's easy to be greedy for MSI-X vectors, but it
really @@ -2022,8 +2022,9 @@ static int
ixgbevf_set_interrupt_capability(struct ixgbevf_adapter *adapter)
 	 * than CPU's.  So let's be conservative and only ask for
 	 * (roughly) twice the number of vectors as there are
CPU's. */
+	ncpu = min_t(int, num_online_cpus(),
DEFAULT_MAX_NUM_RSS_QUEUES); v_budget =
min(adapter->num_rx_queues + adapter->num_tx_queues,
-		       (int)(num_online_cpus() * 2)) +
NON_Q_VECTORS;
+		       ncpu * 2) + NON_Q_VECTORS;
 
 	/* A failure in MSI-X entry allocation isn't fatal, but
it does
 	 * mean we disable MSI-X capabilities of the adapter. */

This change is pointless on the ixgbevf driver.  The VF hardware can
support at most 4 RSS queues.  As such num_rx_queues + num_tx_queues
will never exceed 8 so you are essentially adding a necessary
min(x,8).

It is pointless with the current value, but if someone will edit the
kernel source code and replace the 8 with a 2, it will become
meaningful. The compiler will optimize this part, and I think that for
completion, it is best to keep this reference so a future default
number change will not be missed.

Eilon

I don't feel there is any real point to making this change to the
ixgbevf driver.  82599 virtual functions have 3 MSI-X vectors, one of
which is for the mailbox and the other two can be shared with tx/rx
queue pairs or assigned separately to tx or rx queues.  So this code is
pointless no matter what value is set for DEFAULT_MAX_NUM_RSS_QUEUES.
Perhaps the patches to the other drivers in your RFC will have some
effect but this one looks like a no-op for the ixgbevf driver so there
is no reason for it.

- Greg

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