On Thu, Oct 05, 2017 at 09:28:34AM +0100, Bruce Richardson wrote: > On Thu, Oct 05, 2017 at 01:06:41AM +0100, Ferruh Yigit wrote: > > On 6/3/2017 11:57 PM, Changpeng Liu wrote: > > > For PCI prefetchable resources, Linux will create a > > > write combined file as well, the library will try > > > to map resourceX_wc file first, if the file does > > > not exist, then it will map resourceX as usual. > > > > Hi Changpeng, > > > > Code part looks OK, but can you please describe more why we should try > > write combined resource file first, what is the benefit of using it _wc > > file? > > > > Thanks, > > ferruh > > > Also, if we use a write combining resource file, I believe we will use s/will use/will lose/
> correct ordering of instructions within our drivers. Does applying this > patch not also mean that we would need memory barriers inside all the > drivers, so as to ensure that we don't have a queue doorbell write > reordered with the descriptor writes? I don't think it's safe to apply > this change on it's own, without driver changes, since all PMDs assume > strong ordering on IA. > > Regards, > /Bruce > > > > > > > > > Signed-off-by: Changpeng Liu <[email protected]> > > > --- > > > lib/librte_eal/linuxapp/eal/eal_pci_uio.c | 19 ++++++++++++++----- > > > 1 file changed, 14 insertions(+), 5 deletions(-) > > > > > > diff --git a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c > > > b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c > > > index fa10329..d9fc20a 100644 > > > --- a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c > > > +++ b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c > > > @@ -321,7 +321,7 @@ > > > > > > /* update devname for mmap */ > > > snprintf(devname, sizeof(devname), > > > - "%s/" PCI_PRI_FMT "/resource%d", > > > + "%s/" PCI_PRI_FMT "/resource%d_wc", > > > pci_get_sysfs_path(), > > > loc->domain, loc->bus, loc->devid, > > > loc->function, res_idx); > > > @@ -335,13 +335,22 @@ > > > } > > > > > > /* > > > - * open resource file, to mmap it > > > + * open prefetchable resource file first, try to mmap it > > > */ > > > fd = open(devname, O_RDWR); > > > if (fd < 0) { > > > - RTE_LOG(ERR, EAL, "Cannot open %s: %s\n", > > > - devname, strerror(errno)); > > > - goto error; > > > + snprintf(devname, sizeof(devname), > > > + "%s/" PCI_PRI_FMT "/resource%d", > > > + 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; > > > + } > > > } > > > > > > /* try mapping somewhere close to the end of hugepages */ > > > > >
