Re: [igt-dev] [PATCH i-g-t 01/21] scripts/trace.pl: Fix after intel_engine_notify removal

Tvrtko Ursulin
2019-05-13T12:16:03Z

On 10/05/2019 13:33, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-05-08 13:10:38)
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> After the removal of engine global seqnos and the corresponding
>> intel_engine_notify tracepoints the script needs to be adjusted to cope
>> with the new state of things.
>>
>> To keep working it switches over using the dma_fence:dma_fence_signaled:
>> tracepoint and keeps one extra internal map to connect the ctx-seqno pairs
>> with engines.
>>
>> It also needs to key the completion events on the full engine/ctx/seqno
>> tokens, and adjust correspondingly the timeline sorting logic.
>>
>> v2:
>> * Do not use late notifications (received after context complete) when
>> splitting up coalesced requests. They are now much more likely and can
>> not be used.
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> ---
>> scripts/trace.pl | 82 ++++++++++++++++++++++++------------------------
>> 1 file changed, 41 insertions(+), 41 deletions(-)
>>
>> diff --git a/scripts/trace.pl b/scripts/trace.pl
>> index 18f9f3b18396..95dc3a645e8e 100755
>> --- a/scripts/trace.pl
>> +++ b/scripts/trace.pl
>> @@ -27,7 +27,8 @@ use warnings;
>> use 5.010;
>>
>> my $gid = 0;
>> -my (%db, %queue, %submit, %notify, %rings, %ctxdb, %ringmap, %reqwait, %ctxtimelines);
>> +my (%db, %queue, %submit, %notify, %rings, %ctxdb, %ringmap, %reqwait,
>> + %ctxtimelines, %ctxengines);
>> my @freqs;
>
> So what's ctxengines? Or rings for that matter?

rings go back to the beginnings of the tool when I think the
visualizaiton library needed an unique integer value for every timeline
(so engine). And there is a ringmap from this id back to our engine
name. Perhaps this would be clearer if reversed, but I am not sure how
much churn would that be without actually doing it. Renaming rings to
engines would also make sense.

> I take it ctxengines is really the last engine which we saw this context
> execute on?

Correct.

I guess there is a problem if dma_fence_signaled is delayed past another
request_in. Hm but I also have a die if engine is different.. that
cannot be right, but why it didn't fail.. I need to double check this.

>
>>
>> my $max_items = 3000;
>> @@ -66,7 +67,7 @@ Notes:
>> i915:i915_request_submit, \
>> i915:i915_request_in, \
>> i915:i915_request_out, \
>> - i915:intel_engine_notify, \
>> + dma_fence:dma_fence_signaled, \
>> i915:i915_request_wait_begin, \
>> i915:i915_request_wait_end \
>> [command-to-be-profiled]
>> @@ -161,7 +162,7 @@ sub arg_trace
>> 'i915:i915_request_submit',
>> 'i915:i915_request_in',
>> 'i915:i915_request_out',
>> - 'i915:intel_engine_notify',
>> + 'dma_fence:dma_fence_signaled',
>> 'i915:i915_request_wait_begin',
>> 'i915:i915_request_wait_end' );
>>
>> @@ -312,13 +313,6 @@ sub db_key
>> return $ring . '/' . $ctx . '/' . $seqno;
>> }
>>
>> -sub global_key
>> -{
>> - my ($ring, $seqno) = @_;
>> -
>> - return $ring . '/' . $seqno;
>> -}
>> -
>> sub sanitize_ctx
>> {
>> my ($ctx, $ring) = @_;
>> @@ -419,6 +413,8 @@ while (<>) {
>> $req{'ring'} = $ring;
>> $req{'seqno'} = $seqno;
>> $req{'ctx'} = $ctx;
>> + die if exists $ctxengines{$ctx} and $ctxengines{$ctx} ne $ring;
>> + $ctxengines{$ctx} = $ring;
>> $ctxtimelines{$ctx . '/' . $ring} = 1;
>> $req{'name'} = $ctx . '/' . $seqno;
>> $req{'global'} = $tp{'global'};
>> @@ -429,16 +425,29 @@ while (<>) {
>> $ringmap{$rings{$ring}} = $ring;
>> $db{$key} = \%req;
>> } elsif ($tp_name eq 'i915:i915_request_out:') {
>> - my $gkey = global_key($ring, $tp{'global'});
>> + my $gkey;
>> +
>
> # Must be paired with a previous i915_request_in
>> + die unless exists $ctxengines{$ctx};
>
> I'd suggest next unless, because there's always a change the capture is
> started part way though someone's workload.

That would need much more work.

>
>> + $gkey = db_key($ctxengines{$ctx}, $ctx, $seqno);
>> +
>> + if ($tp{'completed?'}) {
>> + die unless exists $db{$key};
>> + die unless exists $db{$key}->{'start'};
>> + die if exists $db{$key}->{'end'};
>> +
>> + $db{$key}->{'end'} = $time;
>> + $db{$key}->{'notify'} = $notify{$gkey}
>> + if exists $notify{$gkey};
>
> Hmm. With preempt-to-busy, a request can complete when we are no longer
> tracking it (it completes before we preempt it).
>
> They will still get the schedule-out tracepoint, but marked as
> incomplete, and there will be a signaled tp later before we try and
> resubmit.

This sounds like the request would disappear from the scripts view.

>
>> + } else {
>> + delete $db{$key};
>> + }
>> + } elsif ($tp_name eq 'dma_fence:dma_fence_signaled:') {
>> + my $gkey;
>>
>> - die unless exists $db{$key};
>> - die unless exists $db{$key}->{'start'};
>> - die if exists $db{$key}->{'end'};
>> + die unless exists $ctxengines{$tp{'context'}};
>>
>> - $db{$key}->{'end'} = $time;
>> - $db{$key}->{'notify'} = $notify{$gkey} if exists $notify{$gkey};
>> - } elsif ($tp_name eq 'i915:intel_engine_notify:') {
>> - my $gkey = global_key($ring, $seqno);
>> + $gkey = db_key($ctxengines{$tp{'context'}}, $tp{'context'}, $tp{'seqno'});
>>
>> $notify{$gkey} = $time unless exists $notify{$gkey};
>> } elsif ($tp_name eq 'i915:intel_gpu_freq_change:') {
>> @@ -452,7 +461,7 @@ while (<>) {
>> # find the largest seqno to be used for timeline sorting purposes.
>> my $max_seqno = 0;
>> foreach my $key (keys %db) {
>> - my $gkey = global_key($db{$key}->{'ring'}, $db{$key}->{'global'});
>> + my $gkey = db_key($db{$key}->{'ring'}, $db{$key}->{'ctx'}, $db{$key}->{'seqno'});
>>
>> die unless exists $db{$key}->{'start'};
>>
>> @@ -478,14 +487,13 @@ my $key_count = scalar(keys %db);
>>
>> my %engine_timelines;
>>
>> -sub sortEngine {
>> - my $as = $db{$a}->{'global'};
>> - my $bs = $db{$b}->{'global'};
>> +sub sortStart {
>> + my $as = $db{$a}->{'start'};
>> + my $bs = $db{$b}->{'start'};
>> my $val;
>>
>> $val = $as <=> $bs;
>> -
>> - die if $val == 0;
>> + $val = $a cmp $b if $val == 0;
>>
>> return $val;
>> }
>> @@ -497,9 +505,7 @@ sub get_engine_timeline {
>> return $engine_timelines{$ring} if exists $engine_timelines{$ring};
>>
>> @timeline = grep { $db{$_}->{'ring'} eq $ring } keys %db;
>> - # FIXME seqno restart
>> - @timeline = sort sortEngine @timeline;
>> -
>> + @timeline = sort sortStart @timeline;
>> $engine_timelines{$ring} = \@timeline;
>>
>> return \@timeline;
>> @@ -561,20 +567,10 @@ foreach my $gid (sort keys %rings) {
>> $db{$key}->{'no-notify'} = 1;
>> }
>> $db{$key}->{'end'} = $end;
>> + $db{$key}->{'notify'} = $end if $db{$key}->{'notify'} > $end;
>> }
>> }
>>
>> -sub sortStart {
>> - my $as = $db{$a}->{'start'};
>> - my $bs = $db{$b}->{'start'};
>> - my $val;
>> -
>> - $val = $as <=> $bs;
>> - $val = $a cmp $b if $val == 0;
>> -
>> - return $val;
>> -}
>> -
>> my $re_sort = 1;
>> my @sorted_keys;
>>
>> @@ -670,9 +666,13 @@ if ($correct_durations) {
>> next unless exists $db{$key}->{'no-end'};
>> last if $pos == $#{$timeline};
>>
>> - # Shift following request to start after the current one
>> + # Shift following request to start after the current
>> + # one, but only if that wouldn't make it zero duration,
>> + # which would indicate notify arrived after context
>> + # complete.
>> $next_key = ${$timeline}[$pos + 1];
>> - if (exists $db{$key}->{'notify'}) {
>> + if (exists $db{$key}->{'notify'} and
>> + $db{$key}->{'notify'} < $db{$key}->{'end'}) {
>> $db{$next_key}->{'engine-start'} = $db{$next_key}->{'start'};
>> $db{$next_key}->{'start'} = $db{$key}->{'notify'};
>> $re_sort = 1;
>> @@ -750,9 +750,9 @@ foreach my $gid (sort keys %rings) {
>> # Extract all GPU busy intervals and sort them.
>> foreach my $key (@sorted_keys) {
>> next unless $db{$key}->{'ring'} eq $ring;
>> + die if $db{$key}->{'start'} > $db{$key}->{'end'};
>
> Heh, we're out of luck if we want to trace across seqno wraparound.

Yeah, that's another missing thing.

>
> It makes enough sense,
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Thanks. Overall the script could use a cleanup so I'll try to find some
time towards it when this settles.

Regards,

Tvrtko