[dpdk-dev,1/4] igb_uio: add wc option
diff mbox

Message ID 1523455637-31719-2-git-send-email-rk@semihalf.com
State Superseded, archived
Delegated to: Thomas Monjalon
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Context Check Description
ci/checkpatch warning coding style issues
ci/Intel-compilation success Compilation OK

Commit Message

Rafal Kozik April 11, 2018, 2:07 p.m. UTC
Write combining (wc) increase NIC performance by making better
utilization of PCI bus, but cannot be use by all PMD.

Parameter wc_activate add possibility to enable it for
those PMD that could support it.

Signed-off-by: Rafal Kozik <rk@semihalf.com>
---
 kernel/linux/igb_uio/igb_uio.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

Comments

Ferruh Yigit June 27, 2018, 4:34 p.m. UTC | #1
On 4/11/2018 3:07 PM, Rafal Kozik wrote:
> Write combining (wc) increase NIC performance by making better
> utilization of PCI bus, but cannot be use by all PMD.
> 
> Parameter wc_activate add possibility to enable it for
> those PMD that could support it.
> 
> Signed-off-by: Rafal Kozik <rk@semihalf.com>

Hi Rafal,

First, sorry for delayed comment.

> ---
>  kernel/linux/igb_uio/igb_uio.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
> index 4cae4dd..42e3b3f 100644
> --- a/kernel/linux/igb_uio/igb_uio.c
> +++ b/kernel/linux/igb_uio/igb_uio.c
> @@ -30,6 +30,7 @@ struct rte_uio_pci_dev {
>  	int refcnt;
>  };
>  
> +static int wc_activate;
>  static char *intr_mode;
>  static enum rte_intr_mode igbuio_intr_mode_preferred = RTE_INTR_MODE_MSIX;
>  /* sriov sysfs */
> @@ -375,9 +376,13 @@ igbuio_pci_setup_iomem(struct pci_dev *dev, struct uio_info *info,
>  	len = pci_resource_len(dev, pci_bar);
>  	if (addr == 0 || len == 0)
>  		return -1;
> -	internal_addr = ioremap(addr, len);
> -	if (internal_addr == NULL)
> -		return -1;
> +	if (wc_activate == 0) {
> +		internal_addr = ioremap(addr, len);
> +		if (internal_addr == NULL)
> +			return -1;
> +	} else {
> +		internal_addr = NULL;
> +	}

Why we need this update at all?
What is the relation between internal_address and write combined?

As far as I can see we are not using internal_addr at all, what do you observe
in write combined usage without this modification?

>  	info->mem[n].name = name;
>  	info->mem[n].addr = addr;
>  	info->mem[n].internal_addr = internal_addr;
> @@ -638,6 +643,12 @@ MODULE_PARM_DESC(intr_mode,
>  "    " RTE_INTR_MODE_LEGACY_NAME "     Use Legacy interrupt\n"
>  "\n");
>  
> +module_param(wc_activate, int, 0);
> +MODULE_PARM_DESC(wc_activate,
> +"Activate support for write combining (WC) (default=0)\n"
> +"    0 - disable\n"
> +"    other - enable\n");
> +
>  MODULE_DESCRIPTION("UIO driver for Intel IGB PCI cards");
>  MODULE_LICENSE("GPL");
>  MODULE_AUTHOR("Intel Corporation");
>
Rafal Kozik June 28, 2018, 1:08 p.m. UTC | #2
2018-06-27 18:34 GMT+02:00 Ferruh Yigit <ferruh.yigit@intel.com>:
> On 4/11/2018 3:07 PM, Rafal Kozik wrote:
>> Write combining (wc) increase NIC performance by making better
>> utilization of PCI bus, but cannot be use by all PMD.
>>
>> Parameter wc_activate add possibility to enable it for
>> those PMD that could support it.
>>
>> Signed-off-by: Rafal Kozik <rk@semihalf.com>
>
> Hi Rafal,
>
> First, sorry for delayed comment.
>
>> ---
>>  kernel/linux/igb_uio/igb_uio.c | 17 ++++++++++++++---
>>  1 file changed, 14 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
>> index 4cae4dd..42e3b3f 100644
>> --- a/kernel/linux/igb_uio/igb_uio.c
>> +++ b/kernel/linux/igb_uio/igb_uio.c
>> @@ -30,6 +30,7 @@ struct rte_uio_pci_dev {
>>       int refcnt;
>>  };
>>
>> +static int wc_activate;
>>  static char *intr_mode;
>>  static enum rte_intr_mode igbuio_intr_mode_preferred = RTE_INTR_MODE_MSIX;
>>  /* sriov sysfs */
>> @@ -375,9 +376,13 @@ igbuio_pci_setup_iomem(struct pci_dev *dev, struct uio_info *info,
>>       len = pci_resource_len(dev, pci_bar);
>>       if (addr == 0 || len == 0)
>>               return -1;
>> -     internal_addr = ioremap(addr, len);
>> -     if (internal_addr == NULL)
>> -             return -1;
>> +     if (wc_activate == 0) {
>> +             internal_addr = ioremap(addr, len);
>> +             if (internal_addr == NULL)
>> +                     return -1;
>> +     } else {
>> +             internal_addr = NULL;
>> +     }
>
> Why we need this update at all?
> What is the relation between internal_address and write combined?
>
> As far as I can see we are not using internal_addr at all, what do you observe
> in write combined usage without this modification?
>

To get internal_addr memory need to be mapped. But as memory could not be
mapped twice: with and without WC it should be skipped for WC. [1]
WC does not work without this modification.

[1] https://www.kernel.org/doc/ols/2008/ols2008v2-pages-135-144.pdf
        section 5.3 and 5.4

>>       info->mem[n].name = name;
>>       info->mem[n].addr = addr;
>>       info->mem[n].internal_addr = internal_addr;
>> @@ -638,6 +643,12 @@ MODULE_PARM_DESC(intr_mode,
>>  "    " RTE_INTR_MODE_LEGACY_NAME "     Use Legacy interrupt\n"
>>  "\n");
>>
>> +module_param(wc_activate, int, 0);
>> +MODULE_PARM_DESC(wc_activate,
>> +"Activate support for write combining (WC) (default=0)\n"
>> +"    0 - disable\n"
>> +"    other - enable\n");
>> +
>>  MODULE_DESCRIPTION("UIO driver for Intel IGB PCI cards");
>>  MODULE_LICENSE("GPL");
>>  MODULE_AUTHOR("Intel Corporation");
>>
>

Patch
diff mbox

diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
index 4cae4dd..42e3b3f 100644
--- a/kernel/linux/igb_uio/igb_uio.c
+++ b/kernel/linux/igb_uio/igb_uio.c
@@ -30,6 +30,7 @@  struct rte_uio_pci_dev {
 	int refcnt;
 };
 
+static int wc_activate;
 static char *intr_mode;
 static enum rte_intr_mode igbuio_intr_mode_preferred = RTE_INTR_MODE_MSIX;
 /* sriov sysfs */
@@ -375,9 +376,13 @@  igbuio_pci_setup_iomem(struct pci_dev *dev, struct uio_info *info,
 	len = pci_resource_len(dev, pci_bar);
 	if (addr == 0 || len == 0)
 		return -1;
-	internal_addr = ioremap(addr, len);
-	if (internal_addr == NULL)
-		return -1;
+	if (wc_activate == 0) {
+		internal_addr = ioremap(addr, len);
+		if (internal_addr == NULL)
+			return -1;
+	} else {
+		internal_addr = NULL;
+	}
 	info->mem[n].name = name;
 	info->mem[n].addr = addr;
 	info->mem[n].internal_addr = internal_addr;
@@ -638,6 +643,12 @@  MODULE_PARM_DESC(intr_mode,
 "    " RTE_INTR_MODE_LEGACY_NAME "     Use Legacy interrupt\n"
 "\n");
 
+module_param(wc_activate, int, 0);
+MODULE_PARM_DESC(wc_activate,
+"Activate support for write combining (WC) (default=0)\n"
+"    0 - disable\n"
+"    other - enable\n");
+
 MODULE_DESCRIPTION("UIO driver for Intel IGB PCI cards");
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Intel Corporation");