Re: Problem with huge waveforms in EPICS 7

["Zimoch Dirk \(PSI\) via Core-talk" <core-talk at aps.anl.gov>]

On Mon, 2022-06-27 at 15:12 +0200, Zimoch Dirk wrote:
> The problem appears between commit 4ab98081 and 56f05d72. (The two commits in between do not produce stable code.)
> 

Ben did some code refactoring of db_field_log which changed array handling.

In particular in dbEvent.c the following snipped disappeared from db_queue_event_log()

    /*
     * if we have an event on the queue and both the last
     * event on the queue and the current event are emtpy
     * (i.e. of type dbfl_type_rec), simply ignore duplicate
     * events (saving empty events serves no purpose)
     */
    if (pevent->npend > 0u &&
        (*pevent->pLastLog)->type == dbfl_type_rec &&
        pLog->type == dbfl_type_rec) {
        db_delete_field_log(pLog);
        UNLOCKEVQUE (ev_que);
        return;
    }

I have added a debug printf in this code and see that it triggers whenever a frame is dropped. That is about 3 out of 4
frames in my test case.

It is not trivial to put back the code because dbfl_type_rec disappeared from enum dbfl_type too.

I also could not easily revert the merge commit 50419144.

I think Ben's help is needed here.

Dirk