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

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 	 * It's easy to be greedy for MSI-X vectors, but it

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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

Hi Greg,

Since we're changing the RFC to use a new wrapper function which should
replace num_online_cpus (for these purpose), the next RFC version will still
change this driver (for uniformity, if nothing else).

Of course, if you would still have reservations for this change - send them.

Thanks,
Yuval