By default, each device is assumed to be able only handle 64 KB chunks
during DMA. By giving the segment size a larger value, the block layer
will coalesce more S/G entries together for SRP, allowing larger
requests with the same sg_tablesize setting.
This ups the value on Mellanox hardware to 1 GB, corresponding to
reported firmware limits on mlx4.
Signed-off-by: David Dillow <dillo...@ornl.gov>
--
On Tue, 2011-03-22 at 10:01 +0200, Or Gerlitz wrote:
> David Dillow wrote:
> > This ups the value on Mellanox hardware to 2 GB, though there is no HW
> > limit.
>
> You've expressed intention to reduce that value to 1GB as of HW
> limitations, it would also let you get rid from the warnings on the
> current version
>
> > CC [M] drivers/infiniband/hw/mthca/mthca_main.o
> > drivers/infiniband/hw/mthca/mthca_main.c: In function ‘__mthca_init_one’:
> > drivers/infiniband/hw/mthca/mthca_main.c:1047: warning: integer overflow in
> > expression
Well, that's embarrassing. I don't recall seeing those when I tested,
but I don't see how the compiler could have not complained... here's an
updated patch -- against Linus's tree as of a few days ago; work is
currently blocking my git access on wireless. :/
diff --git a/drivers/infiniband/hw/mthca/mthca_main.c
b/drivers/infiniband/hw/mthca/mthca_main.c
index 8a40cd5..f24b79b 100644
--- a/drivers/infiniband/hw/mthca/mthca_main.c
+++ b/drivers/infiniband/hw/mthca/mthca_main.c
@@ -1043,6 +1043,9 @@ static int __mthca_init_one(struct pci_dev *pdev, int
hca_type)
}
}
+ /* We can handle large RDMA requests, so allow larger segments. */
+ dma_set_max_seg_size(&pdev->dev, 1024 * 1024 * 1024);
+
mdev = (struct mthca_dev *) ib_alloc_device(sizeof *mdev);
if (!mdev) {
dev_err(&pdev->dev, "Device struct alloc failed, "
diff --git a/drivers/net/mlx4/main.c b/drivers/net/mlx4/main.c
index 2765a3c..c835011 100644
--- a/drivers/net/mlx4/main.c
+++ b/drivers/net/mlx4/main.c
@@ -1109,6 +1109,9 @@ static int __mlx4_init_one(struct pci_dev *pdev, const
struct pci_device_id *id)
}
}
+ /* Allow large DMA segments, up to the firmware limit of 1 GB */
+ dma_set_max_seg_size(&pdev->dev, 1024 * 1024 * 1024);
+
priv = kzalloc(sizeof *priv, GFP_KERNEL);
if (!priv) {
dev_err(&pdev->dev, "Device struct alloc failed, "
--
Dave Dillow
National Center for Computational Science
Oak Ridge National Laboratory
(865) 241-6602 office
--
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