Summary: Update copyright messages to match the patterns expected by our open source linters.
Reviewed By: chadaustin
Differential Revision: D15105843
fbshipit-source-id: 6c66b4e3a552f9d71e6b43f9a5e6fcda48fd00d9
Summary:
This patch enables BST stats by default, and works as follows:
- it uses quantile stats to maintain per queue per port stats.
- these stats are exposed to ODS.
- experiments showed that a significant CPU cycles were spent in doing
bcm_cosq_bst_stat_sync which syncs the hw stat value to sw copy.
For example, calling bcm_cosq_bst_stat_sync while retrieving BST stats
for for every port/every queue/every second resulted into CPU utilization
going up from ~ 50% for Wedge 100 to ~100-120%. Thus, this patch calls
bcm_cosq_bst_stat_sync only once per minute and then retrieves all BST stats.
- The above optimization also helps when bufferstatlogging is enabled.
- when bufferstatlogging is enabled, the BST stats will be retrieved every
second for scuba logging, and quantile stats will also be exported every
second.
- The bufferstatlogging is enabled using fboss CLI (over thrift).
We no longer need enable_fine_grained_buffer_stats option. But, a new option
viz. update_bststats_interval_s is introduced that keeps the frequency of BST
stats updates configurable.
The virtual memory overhead of always maintaining BST stats is < 5%, and
physical memory overhead is < 0.1%. Thanks to the sync optimization above,
the CPU overhead is negligible. Refer Test Plan for raw data and math.
An alternative is to explore using TimeSeriesMinMax (to maintain max over a
time window) and TLCounter (to expose stats to ODS) instead of quantile stats.
One benefit of using quantile stats is that we don't need to maintain our own
TimeSeriesMinMax but can rely on common facebook wide infra. Moreoever,
quantile stats interface is (arguably) simpler than using combination of
TimeSeriesMinMax + TlCounter'.
A separate diff against configerator is sent out to expose the new bst_stats: D8902636
Differential Revision: D8764329
fbshipit-source-id: 78db3de5340497f2f5780863035dd9ff28dcd79b
