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dpif-netdev: Report overhead busy cycles per pmd.

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Users complained that per rxq pmd usage was confusing: summing those
values per pmd would never reach 100% even if increasing traffic load
beyond pmd capacity.

This is because the dpif-netdev/pmd-rxq-show command only reports "pure"
rxq cycles while some cycles are used in the pmd mainloop and adds up to
the total pmd load.

dpif-netdev/pmd-stats-show does report per pmd load usage.
This load is measured since the last dpif-netdev/pmd-stats-clear call.
On the other hand, the per rxq pmd usage reflects the pmd load on a 10s
sliding window which makes it non trivial to correlate.

Gather per pmd busy cycles with the same periodicity and report the
difference as overhead in dpif-netdev/pmd-rxq-show so that we have all
info in a single command.

Example:
$ ovs-appctl dpif-netdev/pmd-rxq-show
pmd thread numa_id 1 core_id 3:
  isolated : true
  port: dpdk0             queue-id:  0 (enabled)   pmd usage: 90 %
  overhead:  4 %
pmd thread numa_id 1 core_id 5:
  isolated : false
  port: vhost0            queue-id:  0 (enabled)   pmd usage:  0 %
  port: vhost1            queue-id:  0 (enabled)   pmd usage: 93 %
  port: vhost2            queue-id:  0 (enabled)   pmd usage:  0 %
  port: vhost6            queue-id:  0 (enabled)   pmd usage:  0 %
  overhead:  6 %
pmd thread numa_id 1 core_id 31:
  isolated : true
  port: dpdk1             queue-id:  0 (enabled)   pmd usage: 86 %
  overhead:  4 %
pmd thread numa_id 1 core_id 33:
  isolated : false
  port: vhost3            queue-id:  0 (enabled)   pmd usage:  0 %
  port: vhost4            queue-id:  0 (enabled)   pmd usage:  0 %
  port: vhost5            queue-id:  0 (enabled)   pmd usage: 92 %
  port: vhost7            queue-id:  0 (enabled)   pmd usage:  0 %
  overhead:  7 %

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Kevin Traynor <ktraynor@redhat.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>
This commit is contained in:
David Marchand
2021-07-16 18:21:16 +02:00
committed by Ian Stokes
parent 30bfba0249
commit 3222a89d9a
4 changed files with 93 additions and 33 deletions
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7
lib/dpif-netdev-private-thread.h
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@@ -99,13 +99,18 @@ struct dp_netdev_pmd_thread {
long long int next_optimization;
/* End of the next time interval for which processing cycles
are stored for each polled rxq. */
long long int rxq_next_cycle_store;
long long int next_cycle_store;
/* Last interval timestamp. */
uint64_t intrvl_tsc_prev;
/* Last interval cycles. */
atomic_ullong intrvl_cycles;
/* Write index for 'busy_cycles_intrvl'. */
unsigned int intrvl_idx;
/* Busy cycles in last PMD_INTERVAL_MAX intervals. */
atomic_ullong *busy_cycles_intrvl;
/* Current context of the PMD thread. */
struct dp_netdev_pmd_thread_ctx ctx;