[RTEMS Project] #3665: Add low level event recording infrastructure

RTEMS trac trac at rtems.org
Tue Jan 29 12:57:00 UTC 2019

#3665: Add low level event recording infrastructure
 Reporter:  Sebastian Huber  |       Owner:  Sebastian Huber
     Type:  enhancement      |      Status:  assigned
 Priority:  normal           |   Milestone:  5.1
Component:  lib              |     Version:  5
 Severity:  normal           |  Resolution:
 Keywords:                   |  Blocked By:
 Blocking:                   |

Comment (by Sebastian Huber <sebastian.huber@…>):

 In [changeset:"dca618404ee61c1be8a883ddb679889dbfea284b/rtems"
 #!CommitTicketReference repository="rtems"
 Add low level event recording support

 Add low level event recording infrastructure for system and user
 defined events.  The infrastructure is able to record high frequency
 events such as

  * SMP lock acquire/release,
  * interrupt entry/exit,
  * thread switches,
  * UMA zone allocate/free, and
  * Ethernet packet input/output, etc.

 It allows post-mortem analysis in fatal error handlers, e.g. the last
 events are in the record buffer, the newest event overwrites the oldest
 event.  It is possible to detect record buffer overflows for consumers
 that expect a continuous stream of events, e.g. to display the system
 state in real-time.

 The implementation supports high-end SMP machines (more than 1GHz
 processor frequency, more than four processors).

 Add a new API instead. The implementation uses per-processor data
 structures and no atomic read-modify-write operations.  It is uses
 per-processor ring buffers to record the events.

 The CPU counter is used to get the time of events. It is combined with
 periodic uptime events to synchronize it with CLOCK_REALTIME.

 The existing capture engine tries to solve this problem also, but its
 performance is not good enough for high-end production systems.  The
 main issues are the variable-size buffers and the use of SMP locks for
 synchronization.  To fix this, the API would change significantly.

 Update #3665.

Ticket URL: <http://devel.rtems.org/ticket/3665#comment:1>
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