Re: [PATCH v3] audit: report audit wait metric in audit status reply

On Sat, Jul 4, 2020 at 11:15 AM Max Englander <max.englander(a)gmail.com&gt; wrote: > > In environments where the preservation of audit events and predictable > usage of system memory are prioritized, admins may use a combination of > --backlog_wait_time and -b options at the risk of degraded performance > resulting from backlog waiting. In some cases, this risk may be > preferred to lost events or unbounded memory usage. Ideally, this risk > can be mitigated by making adjustments when backlog waiting is detected. > > However, detection can be difficult using the currently available > metrics. For example, an admin attempting to debug degraded performance > may falsely believe a full backlog indicates backlog waiting. It may > turn out the backlog frequently fills up but drains quickly. > > To make it easier to reliably track degraded performance to backlog > waiting, this patch makes the following changes: > > Add a new field backlog_wait_time_total to the audit status reply. > Initialize this field to zero. Add to this field the total time spent > by the current task on scheduled timeouts while the backlog limit is > exceeded. Reset field to zero upon request via AUDIT_SET. > > Tested on Ubuntu 18.04 using complementary changes to the > audit-userspace and audit-testsuite: > - https://github.com/linux-audit/audit-userspace/pull/134 > - https://github.com/linux-audit/audit-testsuite/pull/97 > > Signed-off-by: Max Englander <max.englander(a)gmail.com&gt; > --- > Patch changelogs between v1 and v2: > - Instead of printing a warning when backlog waiting occurs, add > duration of backlog waiting to cumulative sum, and report this > sum in audit status reply. > > Patch changelogs between v2 and v3: > - Rename backlog_wait_sum to backlog_wait_time_actual. > - Drop unneeded and unwanted header flags > AUDIT_FEATURE_BITMAP_BACKLOG_WAIT_SUM and > AUDIT_VERSION_BACKLOG_WAIT_SUM. > - Increment backlog_wait_time_actual counter after every call to > schedule_timeout rather than once after enqueuing (or losing) an > audit record. > - Add support for resetting backlog_wait_time_actual counter to zero > upon request via AUDIT_SET. > > include/uapi/linux/audit.h | 18 +++++++++++------- > kernel/audit.c | 35 +++++++++++++++++++++++++---------- > 2 files changed, 36 insertions(+), 17 deletions(-) This looks okay to me, thanks for the fixes Max. Steve, does the associated userspace patch look okay to you?