diff options
| author | Dave Jiang | 2015-05-19 16:52:04 -0400 |
|---|---|---|
| committer | Jon Mason | 2015-07-04 14:09:24 -0400 |
| commit | a41ef053f700618f5f55a1dd658908a71163400b (patch) | |
| tree | 6dbde672b790ffab2d8a784ed7cbab349afc1307 | |
| parent | 06917f753547e6bba8a5d17f79971d1c071a70dd (diff) | |
NTB: Default to CPU memcpy for performance
Disable DMA usage by default, since the CPU provides much better
performance with write combining. Provide a module parameter to enable
DMA usage when offloading the memcpy is preferred.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
| -rw-r--r-- | drivers/ntb/ntb_transport.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c index 7a765d3230d8..e07b056af3be 100644 --- a/drivers/ntb/ntb_transport.c +++ b/drivers/ntb/ntb_transport.c @@ -88,6 +88,10 @@ static unsigned int copy_bytes = 1024; module_param(copy_bytes, uint, 0644); MODULE_PARM_DESC(copy_bytes, "Threshold under which NTB will use the CPU to copy instead of DMA"); +static bool use_dma; +module_param(use_dma, bool, 0644); +MODULE_PARM_DESC(use_dma, "Use DMA engine to perform large data copy"); + static struct dentry *nt_debugfs_dir; struct ntb_queue_entry { @@ -1589,10 +1593,15 @@ ntb_transport_create_queue(void *data, struct device *client_dev, dma_cap_zero(dma_mask); dma_cap_set(DMA_MEMCPY, dma_mask); - qp->dma_chan = dma_request_channel(dma_mask, ntb_dma_filter_fn, - (void *)(unsigned long)node); - if (!qp->dma_chan) - dev_info(&pdev->dev, "Unable to allocate DMA channel, using CPU instead\n"); + if (use_dma) { + qp->dma_chan = dma_request_channel(dma_mask, ntb_dma_filter_fn, + (void *)(unsigned long)node); + if (!qp->dma_chan) + dev_info(&pdev->dev, "Unable to allocate DMA channel\n"); + } else { + qp->dma_chan = NULL; + } + dev_dbg(&pdev->dev, "Using %s memcpy\n", qp->dma_chan ? "DMA" : "CPU"); for (i = 0; i < NTB_QP_DEF_NUM_ENTRIES; i++) { entry = kzalloc_node(sizeof(*entry), GFP_ATOMIC, node); |