[ovs-build] Failed: ovsrobot/ovs#2919 (series_194987 - fb3c954)

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Tue Aug 11 08:19:44 UTC 2020

Build Update for ovsrobot/ovs

Build: #2919
Status: Failed

Duration: 57 mins and 34 secs
Commit: fb3c954 (series_194987)
Author: Han Zhou
Message: Revert "ovsdb-idl: Fix NULL deref reported by Coverity."

This reverts commit 68bc6f88a3a36549fcd3b6248c25c5e2e6deb8f3.
The commit causes a regression in OVN scale test. ovn-northd's CPU
more than doubled for the test scenario: create and bind 12k ports.
Below are some perf data of ovn-northd when running command:
  ovn-nbctl --wait=sb sync

Before reverting this commit:
-   92.42%     0.62%  ovn-northd  ovn-northd          [.] main
   - 91.80% main
      + 68.93% ovn_db_run (inlined)
      + 22.45% ovsdb_idl_loop_commit_and_wait

After reverting this commit:
-   92.84%     0.60%  ovn-northd  ovn-northd          [.] main
   - 92.24% main
      + 92.03% ovn_db_run (inlined)

Reverting this commit avoided 22.45% of the CPU caused by

The commit changed the logic of ovsdb_idl_txn_write__() by adding
the check "datum->keys && datum->values" before discarding unchanged
data in a transaction. However, it is normal for OVSDB clients (
such as ovn-northd) to try to set columns with same empty data
as it is before the transaction. IDL would discard these changes
and avoid sending big transactions to server (which would end up as
no-op on server side). In the ovn scale test scenario mentioned above,
each iteration of ovn-northd would send a transaction to server that
includes all rows of the huge Port_Binding table, which caused the
significant CPU increase of ovn-northd (and also the OVN SB DB server),
resulted in longer end to end latency of OVN configuration changes.

For the original problem the commit 68bc6f88 was trying to fix, it
doesn't seem to be a real problem. The NULL deref reported by
Coverity may be addressed in a future patch using a different approach,
if necessary.

Cc: William Tu <u9012063 at gmail.com>
Signed-off-by: Han Zhou <hzhou at ovn.org>
Signed-off-by: 0-day Robot <robot at bytheb.org>

View the changeset: https://github.com/ovsrobot/ovs/commit/fb3c9542030f

View the full build log and details: https://travis-ci.org/github/ovsrobot/ovs/builds/716816333?utm_medium=notification&utm_source=email


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