On Fri, Sep 21, 2012 at 02:14:47PM -0400, David Miller wrote: > From: Jon Mason <jon.mason@xxxxxxxxx> > Date: Fri, 21 Sep 2012 11:09:48 -0700 > > > A PCI-Express non-transparent bridge (NTB) is a point-to-point PCIe bus > > connecting 2 systems, providing electrical isolation between the two subsystems. > > A non-transparent bridge is functionally similar to a transparent bridge except > > that both sides of the bridge have their own independent address domains. The > > host on one side of the bridge will not have the visibility of the complete > > memory or I/O space on the other side of the bridge. To communicate across the > > non-transparent bridge, each NTB endpoint has one (or more) apertures exposed to > > the local system. Writes to these apertures are mirrored to memory on the > > remote system. Communications can also occur through the use of doorbell > > registers that initiate interrupts to the alternate domain, and scratch-pad > > registers accessible from both sides. > > > > The NTB device driver is needed to configure these memory windows, doorbell, and > > scratch-pad registers as well as use them in such a way as they can be turned > > into a viable communication channel to the remote system. ntb_hw.[ch] > > determines the usage model (NTB to NTB or NTB to Root Port) and abstracts away > > the underlying hardware to provide access and a common interface to the doorbell > > registers, scratch pads, and memory windows. These hardware interfaces are > > exported so that other, non-mainlined kernel drivers can access these. > > ntb_transport.[ch] also uses the exported interfaces in ntb_hw.[ch] to setup a > > communication channel(s) and provide a reliable way of transferring data from > > one side to the other, which it then exports so that "client" drivers can access > > them. These client drivers are used to provide a standard kernel interface > > (i.e., Ethernet device) to NTB, such that Linux can transfer data from one > > system to the other in a standard way. > > > > Signed-off-by: Jon Mason <jon.mason@xxxxxxxxx> > > I really don't see anything that requires the TX networking processing > to occur in a tasklet. I see no sleeping, strange locking, or > anything like that. > > And if that's the case, it's just pure overhead. Good point. Removed (and I see a nice little perf bump). Thanks, Jon -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
