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77f65ebdca
Changes:
v3->v2: rebase (no other changes)
passes selftest
v2->v1: read f->num_members only once
fix bug: test rollover mode + flag
Minimize packet drop in a fanout group. If one socket is full,
roll over packets to another from the group. Maintain flow
affinity during normal load using an rxhash fanout policy, while
dispersing unexpected traffic storms that hit a single cpu, such
as spoofed-source DoS flows. Rollover breaks affinity for flows
arriving at saturated sockets during those conditions.
The patch adds a fanout policy ROLLOVER that rotates between sockets,
filling each socket before moving to the next. It also adds a fanout
flag ROLLOVER. If passed along with any other fanout policy, the
primary policy is applied until the chosen socket is full. Then,
rollover selects another socket, to delay packet drop until the
entire system is saturated.
Probing sockets is not free. Selecting the last used socket, as
rollover does, is a greedy approach that maximizes chance of
success, at the cost of extreme load imbalance. In practice, with
sufficiently long queues to absorb bursts, sockets are drained in
parallel and load balance looks uniform in `top`.
To avoid contention, scales counters with number of sockets and
accesses them lockfree. Values are bounds checked to ensure
correctness.
Tested using an application with 9 threads pinned to CPUs, one socket
per thread and sufficient busywork per packet operation to limits each
thread to handling 32 Kpps. When sent 500 Kpps single UDP stream
packets, a FANOUT_CPU setup processes 32 Kpps in total without this
patch, 270 Kpps with the patch. Tested with read() and with a packet
ring (V1).
Also, passes psock_fanout.c unit test added to selftests.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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| .. | ||
| breakpoints | ||
| cpu-hotplug | ||
| efivarfs | ||
| ipc | ||
| kcmp | ||
| memory-hotplug | ||
| mqueue | ||
| net-afpacket | ||
| net-socket | ||
| vm | ||
| Makefile | ||
| README.txt | ||
Linux Kernel Selftests The kernel contains a set of "self tests" under the tools/testing/selftests/ directory. These are intended to be small unit tests to exercise individual code paths in the kernel. Running the selftests ===================== To build the tests: $ make -C tools/testing/selftests To run the tests: $ make -C tools/testing/selftests run_tests - note that some tests will require root privileges. To run only tests targetted for a single subsystem: $ make -C tools/testing/selftests TARGETS=cpu-hotplug run_tests See the top-level tools/testing/selftests/Makefile for the list of all possible targets. Contributing new tests ====================== In general, the rules for for selftests are * Do as much as you can if you're not root; * Don't take too long; * Don't break the build on any architecture, and * Don't cause the top-level "make run_tests" to fail if your feature is unconfigured.