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author | Jesper Dangaard Brouer <brouer@redhat.com> | 2017-08-29 16:37:56 +0200 |
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committer | David S. Miller <davem@davemloft.net> | 2017-08-29 10:51:29 -0700 |
commit | f5836ca5e9867fa6ab88cadb9873af56d9ceb589 (patch) | |
tree | 81b8317a3d986fb176b2df280d946bd250e4ad1a /Documentation/hwmon/ucd9200 | |
parent | xdp: make xdp tracepoints report bpf prog id instead of prog_tag (diff) | |
download | linux-dev-f5836ca5e9867fa6ab88cadb9873af56d9ceb589.tar.xz linux-dev-f5836ca5e9867fa6ab88cadb9873af56d9ceb589.zip |
xdp: separate xdp_redirect tracepoint in error case
There is a need to separate the xdp_redirect tracepoint into two
tracepoints, for separating the error case from the normal forward
case.
Due to the extreme speeds XDP is operating at, loading a tracepoint
have a measurable impact. Single core XDP REDIRECT (ethtool tuned
rx-usecs 25) can do 13.7 Mpps forwarding, but loading a simple
bpf_prog at the tracepoint (with a return 0) reduce perf to 10.2 Mpps
(CPU E5-1650 v4 @ 3.60GHz, driver: ixgbe)
The overhead of loading a bpf-based tracepoint can be calculated to
cost 25 nanosec ((1/13782002-1/10267937)*10^9 = -24.83 ns).
Using perf record on the tracepoint event, with a non-matching --filter
expression, the overhead is much larger. Performance drops to 8.3 Mpps,
cost 48 nanosec ((1/13782002-1/8312497)*10^9 = -47.74))
Having a separate tracepoint for err cases, which should be less
frequent, allow running a continuous monitor for errors while not
affecting the redirect forward performance (this have also been
verified by measurements).
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/hwmon/ucd9200')
0 files changed, 0 insertions, 0 deletions