[dpdk-dev] [PATCH v2 3/4] eal: enable WC during resources mapping
Rafał Kozik
rk at semihalf.com
Fri Jun 29 10:58:40 CEST 2018
2018-06-28 16:50 GMT+02:00 Ferruh Yigit <ferruh.yigit at intel.com>:
> On 6/28/2018 2:15 PM, Rafal Kozik wrote:
>> Write combining (WC) increases NIC performance by making better
>> utilization of PCI bus, but cannot be used by all PMDs.
>>
>> It will be enabled only if RTE_PCI_DRV_WC_ACTIVATE will be set in
>> drivers flags. For proper work also igb_uio driver must be loaded with
>> wc_activate set to 1.
>>
>> When mapping PCI resources, firstly try to us WC.
>> If it is not supported it will fallback to normal mode.
>>
>> Signed-off-by: Rafal Kozik <rk at semihalf.com>
>> Acked-by: Bruce Richardson <bruce.richardson at intel.com>
>> ---
>> drivers/bus/pci/linux/pci_uio.c | 41 +++++++++++++++++++++++++++++------------
>> drivers/bus/pci/rte_bus_pci.h | 2 ++
>> 2 files changed, 31 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
>> index d423e4b..e3947c2 100644
>> --- a/drivers/bus/pci/linux/pci_uio.c
>> +++ b/drivers/bus/pci/linux/pci_uio.c
>> @@ -282,22 +282,19 @@ int
>> pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
>> struct mapped_pci_resource *uio_res, int map_idx)
>> {
>> - int fd;
>> + int fd = -1;
>> char devname[PATH_MAX];
>> void *mapaddr;
>> struct rte_pci_addr *loc;
>> struct pci_map *maps;
>> + int wc_activate = 0;
>> +
>> + if (dev->driver != NULL)
>> + wc_activate = dev->driver->drv_flags & RTE_PCI_DRV_WC_ACTIVATE;
>>
>> loc = &dev->addr;
>> maps = uio_res->maps;
>>
>> - /* update devname for mmap */
>> - snprintf(devname, sizeof(devname),
>> - "%s/" PCI_PRI_FMT "/resource%d",
>> - rte_pci_get_sysfs_path(),
>> - loc->domain, loc->bus, loc->devid,
>> - loc->function, res_idx);
>> -
>> /* allocate memory to keep path */
>> maps[map_idx].path = rte_malloc(NULL, strlen(devname) + 1, 0);
>> if (maps[map_idx].path == NULL) {
>> @@ -309,11 +306,31 @@ pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
>> /*
>> * open resource file, to mmap it
>> */
>> - fd = open(devname, O_RDWR);
>> - if (fd < 0) {
>> - RTE_LOG(ERR, EAL, "Cannot open %s: %s\n",
>> + if (wc_activate) {
>> + /* update devname for mmap */
>> + snprintf(devname, sizeof(devname),
>> + "%s/" PCI_PRI_FMT "/resource%d_wc",
>> + rte_pci_get_sysfs_path(),
>> + loc->domain, loc->bus, loc->devid,
>> + loc->function, res_idx);
>> +
>> + fd = open(devname, O_RDWR);
>
> What do you think adding an error log here? If opening resource$_wc fails and
> fallback to resource# file, there won't be any way for user to know about it.
>
This error will be misleading for two reasons:
* even if open return success, it could silently fall-back to non
prefetchable mode,
* NICs could have multiple BARs, but not all support WC. I such case
fails will be desirable.
>> + }
>> +
>> + if (!wc_activate || fd < 0) {
>> + snprintf(devname, sizeof(devname),
>> + "%s/" PCI_PRI_FMT "/resource%d",
>> + rte_pci_get_sysfs_path(),
>> + loc->domain, loc->bus, loc->devid,
>> + loc->function, res_idx);
>> +
>> + /* then try to map resource file */
>> + fd = open(devname, O_RDWR);
>> + if (fd < 0) {
>> + RTE_LOG(ERR, EAL, "Cannot open %s: %s\n",
>> devname, strerror(errno));
>> - goto error;
>> + goto error;
>> + }
>> }
>>
>> /* try mapping somewhere close to the end of hugepages */
>> diff --git a/drivers/bus/pci/rte_bus_pci.h b/drivers/bus/pci/rte_bus_pci.h
>> index 458e6d0..828acc5 100644
>> --- a/drivers/bus/pci/rte_bus_pci.h
>> +++ b/drivers/bus/pci/rte_bus_pci.h
>> @@ -135,6 +135,8 @@ struct rte_pci_bus {
>>
>> /** Device needs PCI BAR mapping (done with either IGB_UIO or VFIO) */
>> #define RTE_PCI_DRV_NEED_MAPPING 0x0001
>> +/** Device needs PCI BAR mapping with enabled write combining (wc) */
>> +#define RTE_PCI_DRV_WC_ACTIVATE 0x0002
>> /** Device driver supports link state interrupt */
>> #define RTE_PCI_DRV_INTR_LSC 0x0008
>> /** Device driver supports device removal interrupt */
>>
>
More information about the dev
mailing list