On Mon, 2011-08-01 at 11:49 -0700, Rick Jones wrote: > On 07/31/2011 11:56 PM, Tom Herbert wrote: > > Describes RSS, RPS, RFS, accelerated RFS, and XPS. > > > > Signed-off-by: Tom Herbert<therbert@xxxxxxxxxx> > > --- > > Documentation/networking/scaling.txt | 346 ++++++++++++++++++++++++++++++++++ > > 1 files changed, 346 insertions(+), 0 deletions(-) > > create mode 100644 Documentation/networking/scaling.txt > > > > diff --git a/Documentation/networking/scaling.txt b/Documentation/networking/scaling.txt > > new file mode 100644 > > index 0000000..aa51f0f > > --- /dev/null > > +++ b/Documentation/networking/scaling.txt > > @@ -0,0 +1,346 @@ > > +Scaling in the Linux Networking Stack > > + > > + > > +Introduction > > +============ > > + > > +This document describes a set of complementary techniques in the Linux > > +networking stack to increase parallelism and improve performance (in > > +throughput, latency, CPU utilization, etc.) for multi-processor systems. > > Why not just leave-out the parenthetical lest some picky pedant find a > specific example where either of those three are not improved? As I'm sure you're aware, there is often a trade-off between throughput and latency. It might be useful to provide some guidelines for optimising each of the above. [...] > > +== RSS IRQ Configuration > > + > > +Each receive queue has a separate IRQ associated with it. The NIC > > +triggers this to notify a CPU when new packets arrive on the given > > +queue. The signaling path for PCIe devices uses message signaled > > +interrupts (MSI-X), that can route each interrupt to a particular CPU. > > +The active mapping of queues to IRQs can be determined from > > +/proc/interrupts. By default, all IRQs are routed to CPU0. Because a > > Really? The default affinity for most IRQs is all-CPUs. At least on x86, that really means CPU 0 only, so far as I can see. [...] > > +== Accelerated RFS Configuration > > + > > +Accelerated RFS is only available if the kernel is compiled with > > +CONFIG_RFS_ACCEL and support is provided by the NIC device and driver. > > +It also requires that ntuple filtering is enabled via ethtool. > > Requires that ntuple filtering be enabled? [...] As a matter of fact, n-tuple filtering is enabled by default where available. So it might actually make more sense to say that RFS acceleration can be *disabled* by disabling n-tuple filtering using ethtool. Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
