[ovs-git] [openvswitch/ovs] 4f9460: ovsdb: Strong references cascade performance fix.

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/openvswitch/ovs
  Commit: 4f94601a9aba0377dc5ec989f197227ac0c9863c
      https://github.com/openvswitch/ovs/commit/4f94601a9aba0377dc5ec989f197227ac0c9863c
  Author: Rodriguez Betancourt, Esteban <estebarb at hpe.com>
  Date:   2016-06-23 (Thu, 23 Jun 2016)

  Changed paths:
    M ovsdb/transaction.c

  Log Message:
  -----------
  ovsdb: Strong references cascade performance fix.

Improves the performance of OVSDB avoiding the chain
reaction produced when modifing rows with a strong
reference and the pointed rows have more strong
references.

The approach taken was using the change bitmap to avoid
triggering a change count when the column hasn't changed.

One way to trigger the issue is emulating a simple linked list
with strong references within a table, where each new row
points to the previous.

Without the fix OVSDB creates a ovsdb_txn_row (and a copy
of the row) for each row in the table.
With the fix it only creates two ovsdb_txn_row: the new row and
the directly pointed row.

Signed-off-by: Esteban Rodriguez Betancourt <estebarb at hpe.com>
Signed-off-by: Ben Pfaff <blp at ovn.org>