[Ovmsdev] OVMS Poller module/singleton
Michael Geddes
frog at bunyip.wheelycreek.net
Sat May 18 08:28:43 HKT 2024
You did say max/pead value. I also halved the N for both.
I'm not sure whether the 'max' should be the maximum of the smoothed
value.. or the maximum of the raw value.
This is currently the raw-value maximum.
The problem is that the middle column is the maximum of the {{sum over 10s}
/ (10*1000,000)
I could easily change the 'period' to 1s and see how that goes.. was just
trying to reduce the larger calculations.
Usage: poller [pause|resume|status|times|trace]
OVMS# poller time status
Poller timing is: on
Type | Count | Ave time | Ave length
| per s | ms per s | ms
-------------+----------+-----------+-----------
Poll:PRI | 1.00| 0.559| 0.543
peak | | 0.663| 1.528
-------------+----------+-----------+-----------
Poll:SRX | 0.08| 0.009| 0.038
peak | | 0.068| 0.146
-------------+----------+-----------+-----------
CAN1 RX[778] | 0.11| 0.061| 0.280
peak | | 0.458| 1.046
-------------+----------+-----------+-----------
CAN1 RX[7a8] | 0.04| 0.024| 0.124
peak | | 0.160| 0.615
-------------+----------+-----------+-----------
CAN1 TX[770] | 0.05| 0.004| 0.016
peak | | 0.022| 0.102
-------------+----------+-----------+-----------
CAN1 TX[7a0] | 0.02| 0.002| 0.011
peak | | 0.010| 0.098
-------------+----------+-----------+-----------
CAN1 TX[7b3] | 0.01| 0.001| 0.006
peak | | 0.000| 0.099
-------------+----------+-----------+-----------
CAN1 TX[7e2] | 0.02| 0.002| 0.011
peak | | 0.010| 0.099
-------------+----------+-----------+-----------
CAN1 TX[7e4] | 0.08| 0.008| 0.048
peak | | 0.049| 0.107
-------------+----------+-----------+-----------
Cmd:State | 0.00| 0.000| 0.005
peak | | 0.000| 0.094
On Fri, 17 May 2024 at 15:26, Michael Geddes <frog at bunyip.wheelycreek.net>
wrote:
> This is what I have now.
> The one on the end is the one MIchael B was after using an N of 32. (up
> for discussion).
>
> The middle is the time spent in that even t per second. It accumulates
> times (in microseconds), and then every 10s it stores it as smoothed (N=16)
> value.
> The Count is similar (except that we store a value of '100' as 1 event so
> it can be still integers and has 2 decimal places).
>
> Every received poll does a 64bit difference to 32bit (for the elapsed
> time) and 64bit comparison (for end-of-period).
> It also does 1x 32bit smoothing and 2x 32bit adds.
>
> Then at the end of a 10s period, it will do a 64bit add to get the next
> end-of-period value, as well as the 2x 32bit smoothing calcs.
>
> This is from the Ioniq 5 so not any big values yet. You can certainly see
> how insignificant the TX callbacks are.
> I'll leave it on for when the car is moving and gets some faster polling.
>
> OVMS# poll time status
> Poller timing is: on
> Type | Count | Ave time | Ave Length
> | per s | ms per s | ms
> -------------+----------+-----------+-----------
> Poll:PRI | 1.00| 0.540| 0.539
> Poll:SRX | 0.03| 0.004| 0.017
> CAN1 RX[778] | 0.06| 0.042| 0.175
> CAN1 TX[770] | 0.04| 0.002| 0.008
> Cmd:State | 0.01| 0.001| 0.005
>
> ----------------------8<--------------------------------
>
> Nice smoothing class (forces N as a power of 2):
> constexpr unsigned floorlog2(unsigned x)
> {
> return x == 1 ? 0 : 1+floorlog2(x >> 1);
> }
> /* Maintain a smoothed average using shifts for division.
> * T should be an integer type
> * N needs to be a power of 2
> */
> template <typename T, unsigned N>
> class average_util_t
> {
> private:
> T m_ave;
> public:
> average_util_t() : m_ave(0) {}
> static const uint8_t _BITS = floorlog2(N);
> void add( T val)
> {
> static_assert(N == (1 << _BITS), "N must be a power of 2");
> m_ave = (((N-1) * m_ave) + val) >> _BITS;
> }
> T get() { return m_ave; }
> operator T() { return m_ave; }
> };
>
>
>
> On Thu, 16 May 2024 at 10:29, Michael Geddes <frog at bunyip.wheelycreek.net>
> wrote:
>
>> Thanks Michael,
>>
>> My calculations give me ((2^32)-1) / (1000*1000*3600) = only 1.2 hours of
>> processing time in 32bit. The initial subtraction is 64bit anyway and I
>> can't see a further 64bit addition being a problem. I have the calculations
>> being performed in doubles at print-out where performance is not really an
>> issue anyway. (Though apparently doing 64 bit division is worse than
>> floating point).
>>
>> In addition
>> * I currently have this being able to be turned on and off and reset
>> manually (only do it when required).
>>
>> * For the lower volume commands, the smoothed average is not going to be
>> useful - the count is more interesting for different reasons.
>>
>> * The total time is quite useful. Ie a high average time doesn't matter
>> if the count is low. The things that are affecting performance are stuff
>> with high total time. Stuff which is happening 100 times a second needs to
>> be a much lower average than once a second.
>>
>> * A measure like 'time per minute/second' and possibly count per
>> minute/seconds as a smoothed average would potentially be more useful. (or
>> in addition?)
>> I think we could do _that_ in a reasonably efficient manner using a 64
>> bit 'last measured time', a 32 bit accumulated value and the stored 32 bit
>> rolling average.
>> It would boils down to some iterative (integer) sums and multiplications
>> plus a divide by n ^ (time periods passed) - which is a shift - and which
>> can be optimised to '0' if 'time-periods-passed' is more than
>> 32/(bits-per-n) - effectively limiting the number of iterations.
>> The one issue I can see is that we need to calculate 'number of
>> time-periods passed' which is a 64 bit subtraction followed by a 32 bit
>> division (not optimisable to a simple shift).
>>
>> * I'm also happy to keep a rolling (32bit) average time.
>> Even if you assume averages in the 100ms, 32bit is going to happily
>> support an N of 64 or even 128.
>> Am I right in thinking that the choice of N is highly dependent on
>> frequency. For things happening 100 times per second, you might want an N
>> like 128.. where things happening once per
>> second, you might want an N of 4 or 8. The other things we keep track
>> of in this manner we have a better idea of the frequency of the thing.
>>
>> How about we have (per record type):
>> * total count (since last reset?) (32 bit)
>> * smoothed average of time per instance (32 bit)
>>
>> * ?xx? total accumulated time since last reset (64bit) ?? <-- with the
>> below stats this is much less useful
>>
>> * last-measured-time (64 bit)
>> * accumulated count since last time-period (16bit - but maybe 32bit
>> anyway for byte alignment?)
>> * smoothed average of count per time-period (32bit)
>> * accumulated time since last time-period (32bit)
>> * smoothed average of time per time-period (32bit)
>>
>> It's possible to keep the
>>
>> Is this going to be too much per record type? The number of 'records' we
>> are keeping is quite low (so 10 to 20 maybe) - so it's not a huge memory
>> burden.
>>
>> Thoughts?
>>
>> //.ichael
>> On Thu, 16 May 2024 at 03:09, Michael Balzer via OvmsDev <
>> ovmsdev at lists.openvehicles.com> wrote:
>>
>>> esp_timer_get_time() is the right choice for precision timing.
>>>
>>> I'd say uint32 is enough though, even if counting microseconds that can
>>> hold a total of more than 71 hours of actual processing time. uint64 has a
>>> significant performance penalty, although I don't recall the overhead for
>>> simple additions.
>>>
>>> Also & more important, the average wouldn't be my main focus, but the
>>> maximum processing time seen per ID, which seems to be missing in your
>>> draft.
>>>
>>> Second thought on the average… the exact overall average really has a
>>> minor meaning, I'd rather see the current average, adapting to the current
>>> mode of operation (drive/charge/…). I suggest feeding the measurements to a
>>> low pass filter to get the smoothed average of the last n measurements.
>>> Pattern:
>>>
>>> runavg = ((N-1) * runavg + newval) / N
>>>
>>> By using a low power of 2 for N (e.g. 8 or 16), you can replace the
>>> division by a simple bit shift, and have enough headroom to use 32 bit
>>> integers.
>>>
>>> Regards,
>>> Michael
>>>
>>>
>>> Am 15.05.24 um 06:51 schrieb Michael Geddes via OvmsDev:
>>>
>>> Formatting aside, I have implemented what I think Michael B was
>>> suggesting. This is a sample run on the Ioniq 5 (which doesn't have
>>> unsolicited RX events).
>>>
>>> This uses the call esp_timer_get_time() got get a 64bit *microseconds*
>>> since started value - and works out the time to execute that way. It's
>>> looking at absolute time and not time in the Task - so other things going
>>> on at the same time in other tasks will have an effect. (The normal tick
>>> count doesn't have nearly enough resolution to be useful - any other ideas
>>> on measurement?) I've got total accumulated time displaying in seconds and
>>> the average in milliseconds currently - but I can change that easy enough.
>>> The cumulative time is stored as uint64_t which will be plenty, as 32bit
>>> wouldn't be nearly enough.
>>>
>>> OVMS# *poller time on*
>>> Poller timing is now on
>>>
>>> OVMS# *poller time status*
>>> Poller timing is: on
>>> Poll [PRI] : n=390 tot=0.2s ave=0.586ms
>>> Poll [SRX] : n=316 tot=0.1s ave=0.196ms
>>> CAN1 RX[0778] : n=382 tot=0.2s ave=0.615ms
>>> CAN1 RX[07a8] : n=48 tot=0.0s ave=0.510ms
>>> CAN1 RX[07bb] : n=162 tot=0.1s ave=0.519ms
>>> CAN1 RX[07ce] : n=33 tot=0.0s ave=0.469ms
>>> CAN1 RX[07ea] : n=408 tot=0.2s ave=0.467ms
>>> CAN1 RX[07ec] : n=486 tot=0.2s ave=0.477ms
>>> CAN3 RX[07df] : n=769 tot=0.2s ave=0.261ms
>>> CAN1 TX[0770] : n=191 tot=0.0s ave=0.054ms
>>> CAN1 TX[07a0] : n=16 tot=0.0s ave=0.047ms
>>> CAN1 TX[07b3] : n=31 tot=0.0s ave=0.069ms
>>> CAN1 TX[07c6] : n=11 tot=0.0s ave=0.044ms
>>> CAN1 TX[07e2] : n=82 tot=0.0s ave=0.067ms
>>> CAN1 TX[07e4] : n=54 tot=0.0s ave=0.044ms
>>> Set State : n=7 tot=0.0s ave=0.104ms
>>>
>>> This is probably going to be quite useful in general! The TX call-backs
>>> don't seem to be significant here. (oh, I should probably implement a reset
>>> of the values too).
>>>
>>> //.ichael
>>>
>>> On Sun, 12 May 2024 at 22:58, Michael Geddes <
>>> frog at bunyip.wheelycreek.net> wrote:
>>>
>>>> Yeah - I certainly wasn't going to put a hard limit. Just a log above a
>>>> certain time, that being said, the idea of just collecting stats (being
>>>> able to turn it on via a "poller timer" set of commands) would be much
>>>> more useful. I'll look into that.
>>>>
>>>> Average time is probably a good stat - and certainly what we care about.
>>>>
>>>> I actually am hopeful that those couple of things I did might help
>>>> reduce that average time quite a bit (that short-cutting the isotp protocol
>>>> handling especially).
>>>>
>>>> That p/r with logging changes might help reduce the unproductive log
>>>> time further, but also makes it possible to turn on the poller logging
>>>> without the RX task logs kicking in.
>>>>
>>>> //.ichael
>>>>
>>>>
>>>> On Sun, 12 May 2024 at 22:29, Michael Balzer via OvmsDev <
>>>> ovmsdev at lists.openvehicles.com> wrote:
>>>>
>>>>> Warning / gathering debug statistics about slow processing can be
>>>>> helpful, but there must not be a hard limit. Frame/poll response processing
>>>>> may need disk or network I/O, and the vehicle task may be starving from
>>>>> punctual high loads on higher priority tasks (e.g. networking) or by
>>>>> needing to wait for some semaphore -- that's outside the application's
>>>>> control, and must not lead to termination/recreation of the task (in case
>>>>> you're heading towards that direction).
>>>>>
>>>>> I have no idea how much processing time the current vehicles actually
>>>>> need in their respective worst cases. Your draft is probably too lax, poll
>>>>> responses and frames normally need to be processed much faster. I'd say 10
>>>>> ms is already too slow, but any wait for a queue/semaphore will already
>>>>> mean at least 10 ms (FreeRTOS tick). Probably best to begin with just
>>>>> collecting stats.
>>>>>
>>>>> Btw, to help in narrowing down the actual problem case, the profiler
>>>>> could collect max times per RX message ID.
>>>>>
>>>>> Regards,
>>>>> Michael
>>>>>
>>>>>
>>>>> Am 12.05.24 um 10:41 schrieb Michael Geddes:
>>>>>
>>>>> I have a question for Michael B (or whoever) - I have a commit lined
>>>>> up that would add a bit of a time check to the poller loop. What do we
>>>>> expect the maximum time to execute a poller loop command should be?
>>>>> This is a rough idea (in ms) I have.. based on nothing much really, so
>>>>> any ideas would be appreciated:
>>>>> int TardyMaxTime_ms(OvmsPoller::OvmsPollEntryType entry_type)
>>>>> {
>>>>> switch (entry_type)
>>>>> {
>>>>> case OvmsPoller::OvmsPollEntryType::Poll: return 80;
>>>>> case OvmsPoller::OvmsPollEntryType::FrameRx: return 30;
>>>>> case OvmsPoller::OvmsPollEntryType::FrameTx: return 20;
>>>>> case OvmsPoller::OvmsPollEntryType::Command: return 10;
>>>>> case OvmsPoller::OvmsPollEntryType::PollState: return 15;
>>>>> default: return 80;
>>>>> }
>>>>> }
>>>>>
>>>>> //.ichael
>>>>>
>>>>> On Mon, 6 May 2024 at 07:45, Michael Geddes <
>>>>> frog at bunyip.wheelycreek.net> wrote:
>>>>>
>>>>>> I realise that I was only using the standard cable to test - which
>>>>>> probably is not sufficient - I haven't looked closely at how the Leaf OBD
>>>>>> to Db9 cable is different from standard.
>>>>>>
>>>>>> Ah, my bad out the queue length. We are definitely queueing more
>>>>>> messages though. From my log of when the overflow happened, the poller
>>>>>> was in state 0 which means OFF - ie nothing was being sent!!
>>>>>>
>>>>>> I'll look at the TX message thing - opt in sounds good - though it
>>>>>> shouldn't be playing that much of a part here as the TXs are infrequent in
>>>>>> this case (or zero when the leaf is off or driving) - On the ioniq 5 when
>>>>>> I'm using the HUD - I'm polling quite frequently - multiple times per
>>>>>> second and that seems to be fine!.
>>>>>>
>>>>>> I did find an issue with the throttling .. but it would still mostly
>>>>>> apply the throttling where it matters, so again, it shouldn't be the
>>>>>> problem (also, we aren't transmitting in the leaf case).
>>>>>>
>>>>>> The change I made to the logging of RX messages showed how many in a
>>>>>> row were dropped... and it was mostly 1 only in a run - which means even if
>>>>>> it is a short time between - that means that the drops are being
>>>>>> interleaved by at least one success!
>>>>>>
>>>>>> Sooo.. I'm still wondering what is going on. Some things I'm going
>>>>>> to try:
>>>>>>
>>>>>> * If the number of messages on the Can bus (coming in through RX)
>>>>>> means that the queue is slowly getting longer and not quite catching up,
>>>>>> then making the queue longer will help it last longer... but only pushes
>>>>>> the problem down the road.
>>>>>> - Add 'current queue length' to the poller status information to
>>>>>> see if this is indeed the case?
>>>>>> - Add some kind of alert when the queue reaches a % full?
>>>>>> * Once you start overflowing and getting overflow log messages, I
>>>>>> wonder if this is then contributing to the problem.
>>>>>> - Push the overflow logging into Poller Task which can look at how
>>>>>> many drops occurred since last received item.
>>>>>> * Split up the flags for the poller messages into 2:
>>>>>> - Messages that are/could be happening in the TX/RX tasks
>>>>>> - Other noisy messages that always happen in the poller task.
>>>>>>
>>>>>> Thoughts on what else we might measure to figure out what is going on?
>>>>>>
>>>>>> //.ichael
>>>>>>
>>>>>>
>>>>>> On Sun, 5 May 2024, 19:29 Michael Balzer via OvmsDev, <
>>>>>> ovmsdev at lists.openvehicles.com> wrote:
>>>>>>
>>>>>>> Michael,
>>>>>>>
>>>>>>> the queue size isn't in bytes, it's in messages:
>>>>>>>
>>>>>>> * @param uxQueueLength The maximum number of items that the queue
>>>>>>> can contain.
>>>>>>> *
>>>>>>> * @param uxItemSize The number of bytes each item in the queue will
>>>>>>> require.
>>>>>>>
>>>>>>>
>>>>>>> Also, from the time stamps in Dereks log excerpt, there were quite
>>>>>>> some dropped frames in that time window -- at least 23 frames in 40 ms,
>>>>>>> that's bad.
>>>>>>>
>>>>>>> Queue sizes are currently:
>>>>>>>
>>>>>>> CONFIG_OVMS_HW_CAN_RX_QUEUE_SIZE=60
>>>>>>> CONFIG_OVMS_VEHICLE_CAN_RX_QUEUE_SIZE=60
>>>>>>>
>>>>>>> The new poller now channels all TX callbacks through the task queue
>>>>>>> additionally to RX and commands. So setting the queue size to be larger
>>>>>>> than the CAN RX queue size seems appropriate.
>>>>>>>
>>>>>>> Nevertheless, an overflow with more than 60 waiting messages still
>>>>>>> indicates some too long processing time in the vehicle task.
>>>>>>>
>>>>>>> TX callbacks previously were done directly in the CAN context, and
>>>>>>> no current vehicle overrides the empty default handler, so this imposed
>>>>>>> almost no additional overhead. By requiring a queue entry for each TX
>>>>>>> callback, this feature now has a potentially high impact for all vehicles.
>>>>>>> If passing these to the task is actually necessary, it needs to become an
>>>>>>> opt-in feature, so only vehicles subscribing to the callback actually need
>>>>>>> to cope with that additional load & potential processing delays involved.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Michael
>>>>>>>
>>>>>>>
>>>>> --
>>>>> Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
>>>>> Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
>>>>>
>>>>> _______________________________________________
>>>>> OvmsDev mailing list
>>>>> OvmsDev at lists.openvehicles.com
>>>>> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
>>>>>
>>>>
>>> _______________________________________________
>>> OvmsDev mailing listOvmsDev at lists.openvehicles.comhttp://lists.openvehicles.com/mailman/listinfo/ovmsdev
>>>
>>>
>>> --
>>> Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
>>> Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
>>>
>>> _______________________________________________
>>> OvmsDev mailing list
>>> OvmsDev at lists.openvehicles.com
>>> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
>>>
>>
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