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authorDavid Dillow <dillowda@ornl.gov>2011-01-17 02:09:44 +0000
committerRoland Dreier <roland@purestorage.com>2011-03-22 09:39:18 -0700
commit7f9e5c48c1078507747434d4c182ab10925bf98a (patch)
tree7be46b01df63e36cee9f17ec6bf9b0910be321c2 /drivers/infiniband
parent1eba843dd7678b9033a0d1ccff21c21b857de77b (diff)
IB: Increase DMA max_segment_size on Mellanox hardware
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. The block layer is the only direct user of it, though a few IOMMU drivers reference it as well for their *_map_sg coalescing code. pci-gart_64 on x86, and a smattering on on sparc, powerpc, and ia64. Since other IB protocols could potentially see larger segments with this, let's check those: - iSER is fine, because you limit your maximum request size to 512 KB, so we'll never overrun the page vector in struct iser_page_vec (128 entries currently). It is independent of the DMA segment size, and handles multi-page segments already. - IPoIB is fine, as it maps each page individually, and doesn't use ib_dma_map_sg(). - RDS appears to do the right thing and has no dependencies on DMA segment size, but I don't claim to have done a complete audit. - NFSoRDMA and 9p are OK -- they do not use ib_dma_map_sg(), so they doesn't care about the coalescing. - Lustre's ko2iblnd does not care about coalescing -- it properly walks the returned sg list. This patch ups the value on Mellanox hardware to 1 GB, which matches reported firmware limits on mlx4. Signed-off-by: David Dillow <dillowda@ornl.gov> Signed-off-by: Roland Dreier <roland@purestorage.com>
Diffstat (limited to 'drivers/infiniband')
-rw-r--r--drivers/infiniband/hw/mthca/mthca_main.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/infiniband/hw/mthca/mthca_main.c b/drivers/infiniband/hw/mthca/mthca_main.c
index 8a40cd539ab..f24b79b805f 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, "