[PATCH/RFC] mlx4_core: module param to limit msix vec allocation

[PATCH/RFC] mlx4_core: module param to limit msix vec allocation

[Arthur Kepner]

The mlx4_core driver allocates 'nreq' msix vectors (and irqs), 
where:

  nreq = min_t(int, dev->caps.num_eqs - dev->caps.reserved_eqs,
               num_possible_cpus() + 1);

ConnectX HCAs support 512 event queues (4 reserved). On a system 
with enough processors, we get:

  mlx4_core 0006:01:00.0: Requested 508 vectors, but only 256 MSI-X vectors available, trying again

Further attempts (by other drivers) to allocate interrupts fail, 
because mlx4_core got 'em all.

How about this?

Signed-off-by: Arthur Kepner <akepner-sJ/iWh9BUns@public.gmane.org>

---

 main.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/net/mlx4/main.c b/drivers/net/mlx4/main.c
index e3e0d54..0a316d0 100644
--- a/drivers/net/mlx4/main.c
+++ b/drivers/net/mlx4/main.c
@@ -68,6 +68,10 @@ static int msi_x = 1;
 module_param(msi_x, int, 0444);
 MODULE_PARM_DESC(msi_x, "attempt to use MSI-X if nonzero");
 
+static int max_msi_x_vec = 64;
+module_param(max_msi_x_vec, int, 0444);
+MODULE_PARM_DESC(max_msi_x_vec, "max MSI-X vectors we'll attempt to allocate");
+
 #else /* CONFIG_PCI_MSI */
 
 #define msi_x (0)
@@ -968,8 +972,10 @@ static void mlx4_enable_msi_x(struct mlx4_dev *dev)
 	int i;
 
 	if (msi_x) {
+		nreq = min_t(int, num_possible_cpus() + 1, max_msi_x_vec);
 		nreq = min_t(int, dev->caps.num_eqs - dev->caps.reserved_eqs,
-			     num_possible_cpus() + 1);
+			     nreq);
+
 		entries = kcalloc(nreq, sizeof *entries, GFP_KERNEL);
 		if (!entries)
 			goto no_msi;
--
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Re: [PATCH/RFC] mlx4_core: module param to limit msix vec allocation

[Eli Cohen]

On Thu, Jun 10, 2010 at 09:59:21AM -0700, Arthur Kepner wrote:
> 
> The mlx4_core driver allocates 'nreq' msix vectors (and irqs), 
> where:
> 
>   nreq = min_t(int, dev->caps.num_eqs - dev->caps.reserved_eqs,
>                num_possible_cpus() + 1);
> 
> ConnectX HCAs support 512 event queues (4 reserved). On a system 
> with enough processors, we get:
> 
>   mlx4_core 0006:01:00.0: Requested 508 vectors, but only 256 MSI-X vectors available, trying again
> 
> Further attempts (by other drivers) to allocate interrupts fail, 
> because mlx4_core got 'em all.
> 
> How about this?
> 

Hi Arthur,

how many CPU cores are in your system? What kernel version did you
use?
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Re: [PATCH/RFC] mlx4_core: module param to limit msix vec allocation

[Arthur Kepner]

On Sun, Jun 13, 2010 at 09:53:24AM +0300, Eli Cohen wrote:
> ....
> how many CPU cores are in your system? What kernel version did you
> use?

I'm almost certain that it was a 2048 core system (it's not available 
right now for me to verify).

We used 2.6.32.12 (sles11 sp1).

-- 
Arthur
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RE: [PATCH/RFC] mlx4_core: module param to limit msix vec allocation

[Yevgeny Petrilin]

 

> The mlx4_core driver allocates 'nreq' msix vectors (and irqs),
> where:
> 
> nreq = min_t(int, dev->caps.num_eqs - dev->caps.reserved_eqs,
>               num_possible_cpus() + 1);
>
> ConnectX HCAs support 512 event queues (4 reserved). On a system with enough processors, we get:
>
>  mlx4_core 0006:01:00.0: Requested 508 vectors, but only 256 MSI-X vectors available, trying again
>
> Further attempts (by other drivers) to allocate interrupts fail, because mlx4_core got 'em all.
>
> How about this?

Hi,
I think that this patch would do the job,
Anyway we are thinking of ways to change our interrupt allocation scheme.

--Yevgeny--
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Re: [PATCH/RFC] mlx4_core: module param to limit msix vec allocation

[Arthur Kepner]

On Thu, Jun 17, 2010 at 05:53:58PM +0300, Yevgeny Petrilin wrote:
> I think that this patch would do the job,

(Is that an ack?)

> Anyway we are thinking of ways to change our interrupt allocation scheme.
> 

Would be interested to know what you've got in mind.

-- 
Arthur
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