Messages in this thread | | | Subject | Re: [PATCH net-next v6 3/9] kbuild: document RPS/XPS network Kconfig options | From | Ben Hutchings <> | Date | Wed, 16 Nov 2011 23:12:02 +0000 |
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On Wed, 2011-11-16 at 14:15 -0800, David Decotigny wrote: > This adds a description of RPS/XPS options and allow them to be > changed at make menuconfig time.
I'm not sure why you think this is necessary.
[...] > config RPS > - boolean > + boolean "Enable Receive Packet Steering" > depends on SMP && SYSFS && USE_GENERIC_SMP_HELPERS > default y > + help > + RPS distributes the load of received packet processing > + across multiple CPUs. If unsure, say Y. > > config RFS_ACCEL > - boolean > + boolean "Enable Hardware Acceleration of RFS" > depends on RPS && GENERIC_HARDIRQS > select CPU_RMAP > default y > + help > + This is the hardware version of RPS. On multi-queue network > + devices, this configures the hardware to distribute the > + received packets across multiple CPUs. If unsure, say Y. [...]
There is some confusion/conflation between RPS and RFS in both code and documentation.
RPS originaly referred to spreading out RX packet processing based on a flow hash. Most multiqueue devices do this in hardware, which is commonly referred to as RSS. RSS can be enabled independently of any networking core features.
RFS refers to directing RX packet processsing of specific flows based on where the corresponding sockets have been used. RFS acceleration means that the driver and hardware help with this by changing hardware queue selection for specific flows.
The RPS Kconfig option controls both RPS and RFS, and various references to 'RPS' in the code really cover RFS as well.
The RFS_ACCEL Kconfig option enables RFS to support acceleration, and like most offload features it has no effect without a driver that specifically supports that. The option only exists to abstract the slightly odd dependency on GENERIC_HARDIRQS, and I don't think it should be manually controllable.
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.
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