[PATCH v2 14/17] NTB: Improve performance with write combining

Allen Hubbe
2015-05-21T13:27:05Z

From: Dave Jiang <dave.jiang@intel.com>

Changing the memory window BAR mappings to write combining significantly
boosts the performance. We will also use memcpy that utilizies
non-temporal store which showed performance improement when doing
non-cached memcpys.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
drivers/ntb/ntb_transport.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
index 733c0ec..95252ea 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -58,6 +58,7 @@
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/types.h>
+#include <linux/uaccess.h>
#include "linux/ntb.h"
#include "linux/ntb_transport.h"

@@ -990,7 +991,7 @@ static int ntb_transport_probe(struct ntb_client *self, struct ntb_dev *ndev)
if (rc)
goto err1;

- mw->vbase = ioremap(mw->phys_addr, mw->phys_size);
+ mw->vbase = ioremap_wc(mw->phys_addr, mw->phys_size);
if (!mw->vbase) {
rc = -ENOMEM;
goto err1;
@@ -1361,7 +1362,11 @@ static void ntb_tx_copy_callback(void *data)

static void ntb_memcpy_tx(struct ntb_queue_entry *entry, void __iomem *offset)
{
- memcpy_toio(offset, entry->buf, entry->len);
+ /*
+ * Using non-temporal mov to improve performance on non-cached
+ * writes. Even though we aren't actually copying from user space.
+ */
+ __copy_from_user_inatomic_nocache(offset, entry->buf, entry->len);

/* Ensure that the data is fully copied out before setting the flags */
wmb();
--
2.4.0.rc0.43.gcf8a8c6