detached abed7f5

refactor(output): count flip merges in the presentation sink

Output queues are flushed every turn and never merge: drop the dead
overflow-merge path from presented.Queue and the merged_flips stat and
warning from drm and headless. Document the sink warning.
commit
abed7f58aa773b8e7155e9b81f463973711286f9
author
brice · · 2026-10-13 17:58 UTC
parent
c9850c5
signature
GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email
8 files · +49 -75
Unified
UnifiedSplit
M docs/performance.md +3 -2
@@ -66,9 +66,10 @@ Every 10 s, each output logs a `stats` entry for the last interval. The main fie
6666 | `max_flip_to_read_ms` | Longest wait from a flip to NeferWL reading its event |
6767 | `late_fences` | Missed vblanks where the GPU finished too late. Needs `--debug=drm-flip` |
6868 | `redrawn_pixels` | Pixels the renderer drew |
69-| `merged_flips` | Flips merged because wayland was not reading output reports. Headless outputs log `stats` too (`frames`, `merged_flips`) |
7069
71-It also counts `frames`, `flips`, `pending`, `cursor_moves` and `cursor_commits`.
70+It also counts `frames`, `flips`, `pending`, `cursor_moves` and `cursor_commits`. Headless outputs log a `stats` entry too (`output`, `frames`).
71+
72+When outputs report faster than the display loop drains, wayland merges their flips and logs a `wayland` warning at most every 10 s (`merged`: flips merged since the last warning). Presentation feedback of a merged flip is answered as discarded.
7273
7374 To find the cause of missed vblanks:
7475
@@ -66,9 +66,10 @@ Every 10 s, each output logs a `stats` entry for the last interval. The main fie
66 | `max_flip_to_read_ms` | Longest wait from a flip to NeferWL reading its event |66 | `max_flip_to_read_ms` | Longest wait from a flip to NeferWL reading its event |
67 | `late_fences` | Missed vblanks where the GPU finished too late. Needs `--debug=drm-flip` |67 | `late_fences` | Missed vblanks where the GPU finished too late. Needs `--debug=drm-flip` |
68 | `redrawn_pixels` | Pixels the renderer drew |68 | `redrawn_pixels` | Pixels the renderer drew |
69-| `merged_flips` | Flips merged because wayland was not reading output reports. Headless outputs log `stats` too (`frames`, `merged_flips`) |
70 69
71-It also counts `frames`, `flips`, `pending`, `cursor_moves` and `cursor_commits`.70+It also counts `frames`, `flips`, `pending`, `cursor_moves` and `cursor_commits`. Headless outputs log a `stats` entry too (`output`, `frames`).
71+
72+When outputs report faster than the display loop drains, wayland merges their flips and logs a `wayland` warning at most every 10 s (`merged`: flips merged since the last warning). Presentation feedback of a merged flip is answered as discarded.
72 73
73 To find the cause of missed vblanks:74 To find the cause of missed vblanks:
74 75
M internal/adapters/drm/output.go +2 -6
@@ -159,10 +159,7 @@ type Output struct {
159159 traceFlips bool
160160 lastFlipAt time.Duration
161161 flipStats flipStats
162- // mergedFlips counts flips merged because wayland was not reading
163- // reports, reported and reset with the periodic stats.
164- mergedFlips int
165- wantedAt time.Duration
162+ wantedAt time.Duration
166163 // vrrFlipGap is the minimum time between a game frame's flip event
167164 // and the next frame commit under VRR (render.vrr-flip-gap, 0: off);
168165 // flipGapUntil is when the next frame may commit: the gap from the
@@ -1465,8 +1462,7 @@ func (o *Output) Run(ctx context.Context, newRenderer func(w, h int) (ports.Rend
14651462 fs := o.takeFlipStats()
14661463 ev = ev.Int("missed_vblanks", fs.missedVblanks).Float64("max_flip_interval_ms", ms(fs.maxInterval))
14671464 ev = ev.Float64("max_commit_delay_ms", ms(fs.maxCommitDelay)).Float64("max_flip_to_read_ms", ms(fs.maxFlipToRead))
1468- ev = ev.Int("redrawn_pixels", r.TakeRedrawn()).Int("merged_flips", o.mergedFlips)
1469- o.mergedFlips = 0
1465+ ev = ev.Int("redrawn_pixels", r.TakeRedrawn())
14701466 if o.traceFlips {
14711467 ev = ev.Int("late_fences", fs.lateFences)
14721468 }
@@ -159,10 +159,7 @@ type Output struct {
159 traceFlips bool159 traceFlips bool
160 lastFlipAt time.Duration160 lastFlipAt time.Duration
161 flipStats flipStats161 flipStats flipStats
162- // mergedFlips counts flips merged because wayland was not reading162+ wantedAt time.Duration
163- // reports, reported and reset with the periodic stats.
164- mergedFlips int
165- wantedAt time.Duration
166 // vrrFlipGap is the minimum time between a game frame's flip event163 // vrrFlipGap is the minimum time between a game frame's flip event
167 // and the next frame commit under VRR (render.vrr-flip-gap, 0: off);164 // and the next frame commit under VRR (render.vrr-flip-gap, 0: off);
168 // flipGapUntil is when the next frame may commit: the gap from the165 // flipGapUntil is when the next frame may commit: the gap from the
@@ -1465,8 +1462,7 @@ func (o *Output) Run(ctx context.Context, newRenderer func(w, h int) (ports.Rend
1465 fs := o.takeFlipStats()1462 fs := o.takeFlipStats()
1466 ev = ev.Int("missed_vblanks", fs.missedVblanks).Float64("max_flip_interval_ms", ms(fs.maxInterval))1463 ev = ev.Int("missed_vblanks", fs.missedVblanks).Float64("max_flip_interval_ms", ms(fs.maxInterval))
1467 ev = ev.Float64("max_commit_delay_ms", ms(fs.maxCommitDelay)).Float64("max_flip_to_read_ms", ms(fs.maxFlipToRead))1464 ev = ev.Float64("max_commit_delay_ms", ms(fs.maxCommitDelay)).Float64("max_flip_to_read_ms", ms(fs.maxFlipToRead))
1468- ev = ev.Int("redrawn_pixels", r.TakeRedrawn()).Int("merged_flips", o.mergedFlips)1465+ ev = ev.Int("redrawn_pixels", r.TakeRedrawn())
1469- o.mergedFlips = 0
1470 if o.traceFlips {1466 if o.traceFlips {
1471 ev = ev.Int("late_fences", fs.lateFences)1467 ev = ev.Int("late_fences", fs.lateFences)
1472 }1468 }
M internal/adapters/drm/output_test.go +6 -7
@@ -14,7 +14,6 @@ import (
1414 "testing/synctest"
1515 "time"
1616
17- "github.com/bnema/neferwl/internal/adapters/outputkit/presented"
1817 portsmocks "github.com/bnema/neferwl/internal/mocks/ports"
1918 "github.com/bnema/neferwl/internal/ports"
2019 "github.com/bnema/zerowrap"
@@ -356,11 +355,12 @@ func TestReportsKeepEveryFlip(t *testing.T) {
356355 if o.reports.Len() != 2 || o.reports.Unsent()[0].Flip.Seq != 1 || o.reports.Unsent()[1].Flip.Seq != 2 || o.reports.Unsent()[1].Seen[1] != 3 {
357356 t.Fatalf("unsent %+v", o.reports.Unsent())
358357 }
359- for i := range presented.MaxUnsent + 3 {
358+ for i := range 20 {
360359 o.report(&ports.FlipInfo{Seq: uint64(10 + i), Shows: map[ports.WindowID]uint64{}}, seen)
361360 }
362- if o.reports.Len() != presented.MaxUnsent || o.reports.Unsent()[0].Flip.Merged == 0 {
363- t.Fatalf("cap: %d reports, first merged %d", o.reports.Len(), o.reports.Unsent()[0].Flip.Merged)
361+ // The wayland sink alone merges flips: the output queue keeps them all.
362+ if o.reports.Len() != 22 || o.reports.Unsent()[2].Flip.Merged != 0 {
363+ t.Fatalf("%d reports, merged %d", o.reports.Len(), o.reports.Unsent()[2].Flip.Merged)
364364 }
365365 }
366366
@@ -750,7 +750,6 @@ func TestRunTrimsRendererOnStatsTick(t *testing.T) {
750750 var statsLog bytes.Buffer // written by Run's goroutine, read after it ends
751751 o.log = zerowrap.New(zerowrap.Config{Level: "info", Format: "json", Output: &statsLog})
752752 o.flipStats = flipStats{missedVblanks: 3, maxInterval: 50 * time.Millisecond, maxFlipToRead: 25 * time.Millisecond, lateFences: 2}
753- o.mergedFlips = 4
754753 trimmed := make(chan struct{}, 2)
755754 failure := os.ErrInvalid
756755 calls := 0 // Run's goroutine only
@@ -777,12 +776,12 @@ func TestRunTrimsRendererOnStatsTick(t *testing.T) {
777776 t.Fatalf("run: %v", err)
778777 }
779778 // Reported once, then reset. late_fences needs flip tracing.
780- for _, want := range []string{`"message":"stats"`, `"missed_vblanks":3`, `"max_flip_interval_ms":50`, `"max_flip_to_read_ms":25`, `"redrawn_pixels":1234`, `"merged_flips":4`} {
779+ for _, want := range []string{`"message":"stats"`, `"missed_vblanks":3`, `"max_flip_interval_ms":50`, `"max_flip_to_read_ms":25`, `"redrawn_pixels":1234`} {
781780 if !strings.Contains(statsLog.String(), want) {
782781 t.Fatalf("stats entry lacks %s: %s", want, statsLog.String())
783782 }
784783 }
785- if strings.Contains(statsLog.String(), "late_fences") || o.flipStats != (flipStats{}) || o.mergedFlips != 0 {
784+ if strings.Contains(statsLog.String(), "late_fences") || o.flipStats != (flipStats{}) {
786785 t.Fatalf("late fences untraced or stats not reset: %s %+v", statsLog.String(), o.flipStats)
787786 }
788787 }
@@ -14,7 +14,6 @@ import (
14 "testing/synctest"14 "testing/synctest"
15 "time"15 "time"
16 16
17- "github.com/bnema/neferwl/internal/adapters/outputkit/presented"
18 portsmocks "github.com/bnema/neferwl/internal/mocks/ports"17 portsmocks "github.com/bnema/neferwl/internal/mocks/ports"
19 "github.com/bnema/neferwl/internal/ports"18 "github.com/bnema/neferwl/internal/ports"
20 "github.com/bnema/zerowrap"19 "github.com/bnema/zerowrap"
@@ -356,11 +355,12 @@ func TestReportsKeepEveryFlip(t *testing.T) {
356 if o.reports.Len() != 2 || o.reports.Unsent()[0].Flip.Seq != 1 || o.reports.Unsent()[1].Flip.Seq != 2 || o.reports.Unsent()[1].Seen[1] != 3 {355 if o.reports.Len() != 2 || o.reports.Unsent()[0].Flip.Seq != 1 || o.reports.Unsent()[1].Flip.Seq != 2 || o.reports.Unsent()[1].Seen[1] != 3 {
357 t.Fatalf("unsent %+v", o.reports.Unsent())356 t.Fatalf("unsent %+v", o.reports.Unsent())
358 }357 }
359- for i := range presented.MaxUnsent + 3 {358+ for i := range 20 {
360 o.report(&ports.FlipInfo{Seq: uint64(10 + i), Shows: map[ports.WindowID]uint64{}}, seen)359 o.report(&ports.FlipInfo{Seq: uint64(10 + i), Shows: map[ports.WindowID]uint64{}}, seen)
361 }360 }
362- if o.reports.Len() != presented.MaxUnsent || o.reports.Unsent()[0].Flip.Merged == 0 {361+ // The wayland sink alone merges flips: the output queue keeps them all.
363- t.Fatalf("cap: %d reports, first merged %d", o.reports.Len(), o.reports.Unsent()[0].Flip.Merged)362+ if o.reports.Len() != 22 || o.reports.Unsent()[2].Flip.Merged != 0 {
363+ t.Fatalf("%d reports, merged %d", o.reports.Len(), o.reports.Unsent()[2].Flip.Merged)
364 }364 }
365 }365 }
366 366
@@ -750,7 +750,6 @@ func TestRunTrimsRendererOnStatsTick(t *testing.T) {
750 var statsLog bytes.Buffer // written by Run's goroutine, read after it ends750 var statsLog bytes.Buffer // written by Run's goroutine, read after it ends
751 o.log = zerowrap.New(zerowrap.Config{Level: "info", Format: "json", Output: &statsLog})751 o.log = zerowrap.New(zerowrap.Config{Level: "info", Format: "json", Output: &statsLog})
752 o.flipStats = flipStats{missedVblanks: 3, maxInterval: 50 * time.Millisecond, maxFlipToRead: 25 * time.Millisecond, lateFences: 2}752 o.flipStats = flipStats{missedVblanks: 3, maxInterval: 50 * time.Millisecond, maxFlipToRead: 25 * time.Millisecond, lateFences: 2}
753- o.mergedFlips = 4
754 trimmed := make(chan struct{}, 2)753 trimmed := make(chan struct{}, 2)
755 failure := os.ErrInvalid754 failure := os.ErrInvalid
756 calls := 0 // Run's goroutine only755 calls := 0 // Run's goroutine only
@@ -777,12 +776,12 @@ func TestRunTrimsRendererOnStatsTick(t *testing.T) {
777 t.Fatalf("run: %v", err)776 t.Fatalf("run: %v", err)
778 }777 }
779 // Reported once, then reset. late_fences needs flip tracing.778 // Reported once, then reset. late_fences needs flip tracing.
780- for _, want := range []string{`"message":"stats"`, `"missed_vblanks":3`, `"max_flip_interval_ms":50`, `"max_flip_to_read_ms":25`, `"redrawn_pixels":1234`, `"merged_flips":4`} {779+ for _, want := range []string{`"message":"stats"`, `"missed_vblanks":3`, `"max_flip_interval_ms":50`, `"max_flip_to_read_ms":25`, `"redrawn_pixels":1234`} {
781 if !strings.Contains(statsLog.String(), want) {780 if !strings.Contains(statsLog.String(), want) {
782 t.Fatalf("stats entry lacks %s: %s", want, statsLog.String())781 t.Fatalf("stats entry lacks %s: %s", want, statsLog.String())
783 }782 }
784 }783 }
785- if strings.Contains(statsLog.String(), "late_fences") || o.flipStats != (flipStats{}) || o.mergedFlips != 0 {784+ if strings.Contains(statsLog.String(), "late_fences") || o.flipStats != (flipStats{}) {
786 t.Fatalf("late fences untraced or stats not reset: %s %+v", statsLog.String(), o.flipStats)785 t.Fatalf("late fences untraced or stats not reset: %s %+v", statsLog.String(), o.flipStats)
787 }786 }
788 }787 }
M internal/adapters/drm/report.go +2 -5
@@ -10,17 +10,14 @@ import (
1010 // Reports to wayland: what the output shows and has read.
1111
1212 // report queues what the output shows and has read, so replaced client
13-// buffers can be released (see presented.Queue for merging).
13+// buffers can be released (see presented.Queue for coalescing).
1414 func (o *Output) report(flip *ports.FlipInfo, seen map[ports.WindowID]uint64) {
1515 o.capped = false
1616 var reads map[ports.WindowID]uint64
1717 if o.capHidden != nil {
1818 seen, reads, o.capped = o.capHidden(seen)
1919 }
20- if o.reports.Push(ports.OutputPresented{Output: o.conn.name, Flip: flip, Shown: o.shown, Queued: o.queued, Seen: seen, ChildReads: reads}) {
21- o.mergedFlips++
22- o.log.Warn().Str("connector", o.conn.name).Msg("wayland is not reading output reports; flips merged")
23- }
20+ o.reports.Push(ports.OutputPresented{Output: o.conn.name, Flip: flip, Shown: o.shown, Queued: o.queued, Seen: seen, ChildReads: reads})
2421 }
2522
2623 // shownBy returns an immutable snapshot of the content Seq of drawn windows.
@@ -10,17 +10,14 @@ import (
10 // Reports to wayland: what the output shows and has read.10 // Reports to wayland: what the output shows and has read.
11 11
12 // report queues what the output shows and has read, so replaced client12 // report queues what the output shows and has read, so replaced client
13-// buffers can be released (see presented.Queue for merging).13+// buffers can be released (see presented.Queue for coalescing).
14 func (o *Output) report(flip *ports.FlipInfo, seen map[ports.WindowID]uint64) {14 func (o *Output) report(flip *ports.FlipInfo, seen map[ports.WindowID]uint64) {
15 o.capped = false15 o.capped = false
16 var reads map[ports.WindowID]uint6416 var reads map[ports.WindowID]uint64
17 if o.capHidden != nil {17 if o.capHidden != nil {
18 seen, reads, o.capped = o.capHidden(seen)18 seen, reads, o.capped = o.capHidden(seen)
19 }19 }
20- if o.reports.Push(ports.OutputPresented{Output: o.conn.name, Flip: flip, Shown: o.shown, Queued: o.queued, Seen: seen, ChildReads: reads}) {20+ o.reports.Push(ports.OutputPresented{Output: o.conn.name, Flip: flip, Shown: o.shown, Queued: o.queued, Seen: seen, ChildReads: reads})
21- o.mergedFlips++
22- o.log.Warn().Str("connector", o.conn.name).Msg("wayland is not reading output reports; flips merged")
23- }
24 }21 }
25 22
26 // shownBy returns an immutable snapshot of the content Seq of drawn windows.23 // shownBy returns an immutable snapshot of the content Seq of drawn windows.
M internal/adapters/headless/output.go +8 -20
@@ -117,8 +117,6 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
117117 // reports queues what the output read; every report is pushed to the
118118 // sink at once (Push never blocks), so it holds one at most.
119119 var reports presented.Queue
120- // mergedFlips counts flips merged since the last stats line.
121- mergedFlips := 0
122120 var security ports.SecurityState
123121 securityKnown := false
124122 failRequests := func(reason error) {
@@ -310,8 +308,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
310308 if err := r.Trim(clk.Now()); err != nil {
311309 return fmt.Errorf("trim renderer: %w", err)
312310 }
313- opts.Log.Info().Str("output", opts.Name).Int("frames", frame).Int("merged_flips", mergedFlips).Msg("stats")
314- mergedFlips = 0
311+ opts.Log.Info().Str("output", opts.Name).Int("frames", frame).Msg("stats")
315312 continue
316313 case s, ok := <-scenes:
317314 if !ok {
@@ -398,9 +395,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
398395 if !haveScene || !dirty || scene.Off {
399396 // Contents not drawn are still read: report them. An output
400397 // turned off draws nothing.
401- if opts.report(&reports, nil, seen) {
402- mergedFlips++
403- }
398+ opts.report(&reports, nil, seen)
404399 continue
405400 }
406401 dirty = false
@@ -449,9 +444,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
449444 if opts.Presented != nil {
450445 _, reads, _ := pipeline.CapHiddenSeen(seen)
451446 if len(reads) > 0 {
452- if reports.Push(ports.OutputPresented{Output: opts.Name, Seen: seen, ChildReads: reads}) {
453- mergedFlips++
454- }
447+ reports.Push(ports.OutputPresented{Output: opts.Name, Seen: seen, ChildReads: reads})
455448 reports.Flush(opts.Presented)
456449 }
457450 }
@@ -548,9 +541,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
548541 pipeline.EndGate(nil)
549542 requests.List = capture.Waiting(requests.List, scene)
550543 frame++
551- if opts.report(&reports, flipInfo(scene, drawn, table.Kept), seen) {
552- mergedFlips++
553- }
544+ opts.report(&reports, flipInfo(scene, drawn, table.Kept), seen)
554545 if scene.Animating && opts.Frames != nil {
555546 select {
556547 case opts.Frames <- ports.OutputFrame{Output: opts.Name}:
@@ -627,16 +618,13 @@ func writePNGSecure(path string, img image.Image, security ports.SessionSecurity
627618 }
628619
629620 // report queues what the output read, with flip for a drawn frame, and
630-// pushes it to the sink. It reports whether a flip was merged.
631-func (opts Options) report(q *presented.Queue, flip *ports.FlipInfo, seen map[ports.WindowID]uint64) (merged bool) {
621+// pushes it to the sink.
622+func (opts Options) report(q *presented.Queue, flip *ports.FlipInfo, seen map[ports.WindowID]uint64) {
632623 if opts.Presented == nil {
633- return false
634- }
635- if merged = q.Push(ports.OutputPresented{Output: opts.Name, Flip: flip, Seen: seen}); merged {
636- opts.Log.Warn().Str("output", opts.Name).Msg("wayland is not reading output reports; flips merged")
624+ return
637625 }
626+ q.Push(ports.OutputPresented{Output: opts.Name, Flip: flip, Seen: seen})
638627 q.Flush(opts.Presented)
639- return merged
640628 }
641629
642630 // flipInfo describes a drawn frame as a flip at the current CLOCK_MONOTONIC
@@ -117,8 +117,6 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
117 // reports queues what the output read; every report is pushed to the117 // reports queues what the output read; every report is pushed to the
118 // sink at once (Push never blocks), so it holds one at most.118 // sink at once (Push never blocks), so it holds one at most.
119 var reports presented.Queue119 var reports presented.Queue
120- // mergedFlips counts flips merged since the last stats line.
121- mergedFlips := 0
122 var security ports.SecurityState120 var security ports.SecurityState
123 securityKnown := false121 securityKnown := false
124 failRequests := func(reason error) {122 failRequests := func(reason error) {
@@ -310,8 +308,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
310 if err := r.Trim(clk.Now()); err != nil {308 if err := r.Trim(clk.Now()); err != nil {
311 return fmt.Errorf("trim renderer: %w", err)309 return fmt.Errorf("trim renderer: %w", err)
312 }310 }
313- opts.Log.Info().Str("output", opts.Name).Int("frames", frame).Int("merged_flips", mergedFlips).Msg("stats")311+ opts.Log.Info().Str("output", opts.Name).Int("frames", frame).Msg("stats")
314- mergedFlips = 0
315 continue312 continue
316 case s, ok := <-scenes:313 case s, ok := <-scenes:
317 if !ok {314 if !ok {
@@ -398,9 +395,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
398 if !haveScene || !dirty || scene.Off {395 if !haveScene || !dirty || scene.Off {
399 // Contents not drawn are still read: report them. An output396 // Contents not drawn are still read: report them. An output
400 // turned off draws nothing.397 // turned off draws nothing.
401- if opts.report(&reports, nil, seen) {398+ opts.report(&reports, nil, seen)
402- mergedFlips++
403- }
404 continue399 continue
405 }400 }
406 dirty = false401 dirty = false
@@ -449,9 +444,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
449 if opts.Presented != nil {444 if opts.Presented != nil {
450 _, reads, _ := pipeline.CapHiddenSeen(seen)445 _, reads, _ := pipeline.CapHiddenSeen(seen)
451 if len(reads) > 0 {446 if len(reads) > 0 {
452- if reports.Push(ports.OutputPresented{Output: opts.Name, Seen: seen, ChildReads: reads}) {447+ reports.Push(ports.OutputPresented{Output: opts.Name, Seen: seen, ChildReads: reads})
453- mergedFlips++
454- }
455 reports.Flush(opts.Presented)448 reports.Flush(opts.Presented)
456 }449 }
457 }450 }
@@ -548,9 +541,7 @@ func Run(ctx context.Context, opts Options, scenes <-chan ports.Scene, contents
548 pipeline.EndGate(nil)541 pipeline.EndGate(nil)
549 requests.List = capture.Waiting(requests.List, scene)542 requests.List = capture.Waiting(requests.List, scene)
550 frame++543 frame++
551- if opts.report(&reports, flipInfo(scene, drawn, table.Kept), seen) {544+ opts.report(&reports, flipInfo(scene, drawn, table.Kept), seen)
552- mergedFlips++
553- }
554 if scene.Animating && opts.Frames != nil {545 if scene.Animating && opts.Frames != nil {
555 select {546 select {
556 case opts.Frames <- ports.OutputFrame{Output: opts.Name}:547 case opts.Frames <- ports.OutputFrame{Output: opts.Name}:
@@ -627,16 +618,13 @@ func writePNGSecure(path string, img image.Image, security ports.SessionSecurity
627 }618 }
628 619
629 // report queues what the output read, with flip for a drawn frame, and620 // report queues what the output read, with flip for a drawn frame, and
630-// pushes it to the sink. It reports whether a flip was merged.621+// pushes it to the sink.
631-func (opts Options) report(q *presented.Queue, flip *ports.FlipInfo, seen map[ports.WindowID]uint64) (merged bool) {622+func (opts Options) report(q *presented.Queue, flip *ports.FlipInfo, seen map[ports.WindowID]uint64) {
632 if opts.Presented == nil {623 if opts.Presented == nil {
633- return false624+ return
634- }
635- if merged = q.Push(ports.OutputPresented{Output: opts.Name, Flip: flip, Seen: seen}); merged {
636- opts.Log.Warn().Str("output", opts.Name).Msg("wayland is not reading output reports; flips merged")
637 }625 }
626+ q.Push(ports.OutputPresented{Output: opts.Name, Flip: flip, Seen: seen})
638 q.Flush(opts.Presented)627 q.Flush(opts.Presented)
639- return merged
640 }628 }
641 629
642 // flipInfo describes a drawn frame as a flip at the current CLOCK_MONOTONIC630 // flipInfo describes a drawn frame as a flip at the current CLOCK_MONOTONIC
M internal/adapters/headless/output_test.go +1 -1
@@ -237,7 +237,7 @@ func TestRunTrimsRendererOnTick(t *testing.T) {
237237 if got := strings.Count(statsLog.String(), `"message":"stats"`); got != 1 {
238238 t.Fatalf("%d stats entries: %s", got, statsLog.String())
239239 }
240- for _, want := range []string{`"output":"HEADLESS-1"`, `"frames":0`, `"merged_flips":0`} {
240+ for _, want := range []string{`"output":"HEADLESS-1"`, `"frames":0`} {
241241 if !strings.Contains(statsLog.String(), want) {
242242 t.Fatalf("stats entry lacks %s: %s", want, statsLog.String())
243243 }
@@ -237,7 +237,7 @@ func TestRunTrimsRendererOnTick(t *testing.T) {
237 if got := strings.Count(statsLog.String(), `"message":"stats"`); got != 1 {237 if got := strings.Count(statsLog.String(), `"message":"stats"`); got != 1 {
238 t.Fatalf("%d stats entries: %s", got, statsLog.String())238 t.Fatalf("%d stats entries: %s", got, statsLog.String())
239 }239 }
240- for _, want := range []string{`"output":"HEADLESS-1"`, `"frames":0`, `"merged_flips":0`} {240+ for _, want := range []string{`"output":"HEADLESS-1"`, `"frames":0`} {
241 if !strings.Contains(statsLog.String(), want) {241 if !strings.Contains(statsLog.String(), want) {
242 t.Fatalf("stats entry lacks %s: %s", want, statsLog.String())242 t.Fatalf("stats entry lacks %s: %s", want, statsLog.String())
243 }243 }
M internal/adapters/outputkit/presented/queue.go +8 -19
@@ -4,17 +4,14 @@ package presented
44
55 import (
66 "maps"
7- "slices"
87
98 "github.com/bnema/neferwl/internal/ports"
109 )
1110
12-// MaxUnsent bounds reports waiting for wayland; past it the oldest flip is
13-// merged into the next one.
14-const MaxUnsent = 16
15-
16-// Queue holds reports wayland has not read yet. Its owner goroutine is the
17-// only user. The Seen and ChildReads maps of a queued report are immutable
11+// Queue holds the reports an output has not pushed to wayland yet. The owner
12+// goroutine flushes it every loop turn, so it holds the few reports of one
13+// turn; the sink alone bounds what waits for the display loop (and merges
14+// flips when that stalls). Its owner goroutine is the only user. The Seen and ChildReads maps of a queued report are immutable
1815 // snapshots: wayland may still read an earlier report on another goroutine,
1916 // so a snapshot is replaced by a clone when its content changes and an
2017 // unchanged report allocates nothing.
@@ -25,9 +22,8 @@ type Queue struct {
2522
2623 // Push queues r. Its Seen and ChildReads may be the caller's scratch maps:
2724 // the queue keeps snapshots. A flip-less report replaces the newest queued
28-// one when that one has no flip, or keeps its flip; flips are merged only
29-// past MaxUnsent. Push reports whether a flip was merged that way.
30-func (q *Queue) Push(r ports.OutputPresented) (merged bool) {
25+// one when that one has no flip, or keeps its flip; every flip is queued.
26+func (q *Queue) Push(r ports.OutputPresented) {
3127 if !maps.Equal(q.seen, r.Seen) {
3228 q.seen = maps.Clone(r.Seen)
3329 }
@@ -40,21 +36,14 @@ func (q *Queue) Push(r ports.OutputPresented) (merged bool) {
4036 r.Flip = q.unsent[n-1].Flip
4137 }
4238 q.unsent[n-1] = r
43- return false
39+ return
4440 }
4541 q.unsent = append(q.unsent, r)
46- if len(q.unsent) <= MaxUnsent {
47- return false
48- }
49- if old, next := q.unsent[0].Flip, q.unsent[1].Flip; next != nil && old != nil {
50- Merge(old, next)
51- }
52- q.unsent = slices.Delete(q.unsent, 0, 1)
53- return true
5442 }
5543
5644 // Merge folds old into next: next counts it as merged and shows what
5745 // old showed, so feedbacks waiting on old are answered (as discarded).
46+// Wayland's presentation sink uses it when its ring overflows.
5847 func Merge(old, next *ports.FlipInfo) {
5948 next.Merged += 1 + old.Merged
6049 // A snapshot can be shared with previously sent flips. Clone only when
@@ -4,17 +4,14 @@ package presented
4 4
5 import (5 import (
6 "maps"6 "maps"
7- "slices"
8 7
9 "github.com/bnema/neferwl/internal/ports"8 "github.com/bnema/neferwl/internal/ports"
10 )9 )
11 10
12-// MaxUnsent bounds reports waiting for wayland; past it the oldest flip is11+// Queue holds the reports an output has not pushed to wayland yet. The owner
13-// merged into the next one.12+// goroutine flushes it every loop turn, so it holds the few reports of one
14-const MaxUnsent = 1613+// turn; the sink alone bounds what waits for the display loop (and merges
15-14+// flips when that stalls). Its owner goroutine is the only user. The Seen and ChildReads maps of a queued report are immutable
16-// Queue holds reports wayland has not read yet. Its owner goroutine is the
17-// only user. The Seen and ChildReads maps of a queued report are immutable
18 // snapshots: wayland may still read an earlier report on another goroutine,15 // snapshots: wayland may still read an earlier report on another goroutine,
19 // so a snapshot is replaced by a clone when its content changes and an16 // so a snapshot is replaced by a clone when its content changes and an
20 // unchanged report allocates nothing.17 // unchanged report allocates nothing.
@@ -25,9 +22,8 @@ type Queue struct {
25 22
26 // Push queues r. Its Seen and ChildReads may be the caller's scratch maps:23 // Push queues r. Its Seen and ChildReads may be the caller's scratch maps:
27 // the queue keeps snapshots. A flip-less report replaces the newest queued24 // the queue keeps snapshots. A flip-less report replaces the newest queued
28-// one when that one has no flip, or keeps its flip; flips are merged only25+// one when that one has no flip, or keeps its flip; every flip is queued.
29-// past MaxUnsent. Push reports whether a flip was merged that way.26+func (q *Queue) Push(r ports.OutputPresented) {
30-func (q *Queue) Push(r ports.OutputPresented) (merged bool) {
31 if !maps.Equal(q.seen, r.Seen) {27 if !maps.Equal(q.seen, r.Seen) {
32 q.seen = maps.Clone(r.Seen)28 q.seen = maps.Clone(r.Seen)
33 }29 }
@@ -40,21 +36,14 @@ func (q *Queue) Push(r ports.OutputPresented) (merged bool) {
40 r.Flip = q.unsent[n-1].Flip36 r.Flip = q.unsent[n-1].Flip
41 }37 }
42 q.unsent[n-1] = r38 q.unsent[n-1] = r
43- return false39+ return
44 }40 }
45 q.unsent = append(q.unsent, r)41 q.unsent = append(q.unsent, r)
46- if len(q.unsent) <= MaxUnsent {
47- return false
48- }
49- if old, next := q.unsent[0].Flip, q.unsent[1].Flip; next != nil && old != nil {
50- Merge(old, next)
51- }
52- q.unsent = slices.Delete(q.unsent, 0, 1)
53- return true
54 }42 }
55 43
56 // Merge folds old into next: next counts it as merged and shows what44 // Merge folds old into next: next counts it as merged and shows what
57 // old showed, so feedbacks waiting on old are answered (as discarded).45 // old showed, so feedbacks waiting on old are answered (as discarded).
46+// Wayland's presentation sink uses it when its ring overflows.
58 func Merge(old, next *ports.FlipInfo) {47 func Merge(old, next *ports.FlipInfo) {
59 next.Merged += 1 + old.Merged48 next.Merged += 1 + old.Merged
60 // A snapshot can be shared with previously sent flips. Clone only when49 // A snapshot can be shared with previously sent flips. Clone only when
M internal/adapters/outputkit/presented/queue_test.go +19 -15
@@ -56,24 +56,28 @@ func TestQueueKeepsEveryFlip(t *testing.T) {
5656 require.Equal(t, uint64(3), u[1].Seen[1])
5757 }
5858
59-// Past MaxUnsent the oldest flip folds into the next: counted as merged and
60-// its shown windows carried, without mutating a shared Shows snapshot.
61-func TestQueueMergesOldestFlipPastBound(t *testing.T) {
62- var q Queue
59+// Merge folds a flip into the next: counted as merged and its shown windows
60+// carried, without mutating a shared Shows snapshot.
61+func TestMergeCarriesShowsWithoutMutatingSharedSnapshot(t *testing.T) {
6362 shared := map[ports.WindowID]uint64{2: 5}
64- q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: 1, Shows: map[ports.WindowID]uint64{1: 4}}})
65- q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: 2, Shows: shared}})
66- merged := false
67- for i := range MaxUnsent - 1 {
68- merged = q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: uint64(10 + i)}}) || merged
63+ old := &ports.FlipInfo{Seq: 1, Merged: 2, Shows: map[ports.WindowID]uint64{1: 4}}
64+ next := &ports.FlipInfo{Seq: 2, Shows: shared}
65+ Merge(old, next)
66+ require.Equal(t, 3, next.Merged)
67+ require.Equal(t, map[ports.WindowID]uint64{1: 4, 2: 5}, next.Shows)
68+ require.Equal(t, map[ports.WindowID]uint64{2: 5}, shared, "shared snapshot untouched")
69+}
70+
71+// The queue never merges flips: every flip of a turn is pushed to the sink.
72+func TestQueueDoesNotBoundFlips(t *testing.T) {
73+ var q Queue
74+ for i := range 40 {
75+ q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: uint64(i + 1)}})
6976 }
70- require.True(t, merged)
7177 u := q.Unsent()
72- require.Len(t, u, MaxUnsent)
73- require.Equal(t, uint64(2), u[0].Flip.Seq)
74- require.Equal(t, 1, u[0].Flip.Merged)
75- require.Equal(t, map[ports.WindowID]uint64{1: 4, 2: 5}, u[0].Flip.Shows)
76- require.Equal(t, map[ports.WindowID]uint64{2: 5}, shared, "shared snapshot untouched")
78+ require.Len(t, u, 40)
79+ require.Zero(t, u[0].Flip.Merged)
80+ require.Equal(t, uint64(1), u[0].Flip.Seq)
7781 }
7882
7983 func TestQueueFlushPushesInOrderAndEmpties(t *testing.T) {
@@ -56,24 +56,28 @@ func TestQueueKeepsEveryFlip(t *testing.T) {
56 require.Equal(t, uint64(3), u[1].Seen[1])56 require.Equal(t, uint64(3), u[1].Seen[1])
57 }57 }
58 58
59-// Past MaxUnsent the oldest flip folds into the next: counted as merged and59+// Merge folds a flip into the next: counted as merged and its shown windows
60-// its shown windows carried, without mutating a shared Shows snapshot.60+// carried, without mutating a shared Shows snapshot.
61-func TestQueueMergesOldestFlipPastBound(t *testing.T) {61+func TestMergeCarriesShowsWithoutMutatingSharedSnapshot(t *testing.T) {
62- var q Queue
63 shared := map[ports.WindowID]uint64{2: 5}62 shared := map[ports.WindowID]uint64{2: 5}
64- q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: 1, Shows: map[ports.WindowID]uint64{1: 4}}})63+ old := &ports.FlipInfo{Seq: 1, Merged: 2, Shows: map[ports.WindowID]uint64{1: 4}}
65- q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: 2, Shows: shared}})64+ next := &ports.FlipInfo{Seq: 2, Shows: shared}
66- merged := false65+ Merge(old, next)
67- for i := range MaxUnsent - 1 {66+ require.Equal(t, 3, next.Merged)
68- merged = q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: uint64(10 + i)}}) || merged67+ require.Equal(t, map[ports.WindowID]uint64{1: 4, 2: 5}, next.Shows)
68+ require.Equal(t, map[ports.WindowID]uint64{2: 5}, shared, "shared snapshot untouched")
69+}
70+
71+// The queue never merges flips: every flip of a turn is pushed to the sink.
72+func TestQueueDoesNotBoundFlips(t *testing.T) {
73+ var q Queue
74+ for i := range 40 {
75+ q.Push(ports.OutputPresented{Flip: &ports.FlipInfo{Seq: uint64(i + 1)}})
69 }76 }
70- require.True(t, merged)
71 u := q.Unsent()77 u := q.Unsent()
72- require.Len(t, u, MaxUnsent)78+ require.Len(t, u, 40)
73- require.Equal(t, uint64(2), u[0].Flip.Seq)79+ require.Zero(t, u[0].Flip.Merged)
74- require.Equal(t, 1, u[0].Flip.Merged)80+ require.Equal(t, uint64(1), u[0].Flip.Seq)
75- require.Equal(t, map[ports.WindowID]uint64{1: 4, 2: 5}, u[0].Flip.Shows)
76- require.Equal(t, map[ports.WindowID]uint64{2: 5}, shared, "shared snapshot untouched")
77 }81 }
78 82
79 func TestQueueFlushPushesInOrderAndEmpties(t *testing.T) {83 func TestQueueFlushPushesInOrderAndEmpties(t *testing.T) {

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