[openib-general] [PATCH] do not clear ecr on msi-x interrupt

[Michael S. Tsirkin]

Hi!
I notice that ECR is never read on an MSI-X interrupt.
It follows that there is no need to clear ECR.

Unfortunately I dont currently have appropriate hardware
to test this, but I would expect a nice (if possibly small)
performance boost in IP over IB.

Comments are welcome.

mst


Signed-off-by: Michael S. Tsirkin <mst at mellanox.co.il>

Index: infiniband/hw/mthca/mthca_eq.c
===================================================================
--- infiniband/hw/mthca/mthca_eq.c	(revision 1538)
+++ infiniband/hw/mthca/mthca_eq.c	(working copy)
@@ -381,7 +381,6 @@ static irqreturn_t mthca_msi_x_interrupt
 	struct mthca_eq  *eq  = eq_ptr;
 	struct mthca_dev *dev = eq->dev;
 
-	writel(eq->ecr_mask, dev->hcr + MTHCA_ECR_CLR_OFFSET + 4);
 	mthca_eq_int(dev, eq);
 
 	/* MSI-X vectors always belong to us */