Daneel
6b3843e0c6
Root cause (per Opus analysis): UAZoomEnabled() is a synchronous Mach IPC roundtrip to macOS Accessibility server, called 3x per redisplay cycle. At 60fps = 180 IPC roundtrips/second blocking the main thread. Combined with Emacs's inherent O(position) redisplay cost, this compounded into progressive choppy behavior. Fix 1: ns_zoom_enabled_p() caches UAZoomEnabled() for 1 second. Fix 2: ns_zoom_track_completion() rate-limited to 2 Hz. Also includes BUF_CHARS_MODIFF fix (patch 0009) for VoiceOver cache.
118 lines
4.6 KiB
Diff
118 lines
4.6 KiB
Diff
From 9e2b56b7aec560540ef9f49c9444c2c0fc903090 Mon Sep 17 00:00:00 2001
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From: Daneel <daneel@sukany.cz>
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Date: Sun, 1 Mar 2026 05:23:37 +0100
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Subject: [PATCH 11/11] perf: cache UAZoomEnabled() and rate-limit completion
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tracking
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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UAZoomEnabled() performs a synchronous Mach IPC roundtrip to the macOS
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Accessibility server (~50-200 µs per call). With three call sites in
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the redisplay hot path (ns_draw_window_cursor, ns_update_end fallback,
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ns_zoom_track_completion) this adds up to 150-600 µs of IPC overhead
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per redisplay cycle. At 60 fps, that is 9-36 ms/s of pure IPC cost.
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The overhead blocks the main thread, extending the inter-frame interval
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and making cursor movement feel choppy, especially at the end of large
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files where Emacs's own redisplay work is already at its maximum.
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* src/nsterm.m (ns_zoom_cached_enabled, ns_zoom_cache_time): New
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static variables.
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(ns_zoom_enabled_p): New inline wrapper around UAZoomEnabled().
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Caches the result for 1 second using CFAbsoluteTimeGetCurrent(), a
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near-free VDSO call. Zoom state changes only on explicit user action
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in System Settings, so a 1-second TTL is indistinguishable from
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querying on every frame. Replaces all three UAZoomEnabled() call
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sites.
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(ns_zoom_track_completion): Add 500 ms rate limit. Completion
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candidate detection requires FOR_EACH_FRAME iteration and
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Fget_char_property calls. Completion state changes at human
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interaction speed (well below 2 Hz), so 500 ms polling is
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imperceptible while eliminating per-redisplay Lisp overhead.
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---
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src/nsterm.m | 43 ++++++++++++++++++++++++++++++++++++++++---
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1 file changed, 40 insertions(+), 3 deletions(-)
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diff --git a/src/nsterm.m b/src/nsterm.m
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index e3f9466..590287a 100644
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--- a/src/nsterm.m
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+++ b/src/nsterm.m
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@@ -1092,6 +1092,31 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
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ivy-current-match, corfu-current that mark the selected candidate. */
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static bool ns_ax_face_is_selected (Lisp_Object face);
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+/* Cached wrapper around UAZoomEnabled().
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+ UAZoomEnabled() performs a synchronous Mach IPC roundtrip to the
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+ macOS Accessibility server (~50-200 µs per call). With three call
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+ sites in the redisplay hot path the overhead accumulates to
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+ 150-600 µs per frame. Zoom state only changes on explicit user
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+ action in System Settings, so a 1-second TTL is both safe and
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+ indistinguishable from querying on every frame.
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+
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+ Uses CFAbsoluteTimeGetCurrent() (a VDSO read on modern macOS, ~5 ns)
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+ to avoid a second IPC roundtrip for time. */
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+static BOOL ns_zoom_cached_enabled;
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+static CFAbsoluteTime ns_zoom_cache_time;
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+
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+static BOOL
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+ns_zoom_enabled_p (void)
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+{
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+ CFAbsoluteTime now = CFAbsoluteTimeGetCurrent ();
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+ if (now - ns_zoom_cache_time > 1.0)
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+ {
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+ ns_zoom_cached_enabled = UAZoomEnabled ();
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+ ns_zoom_cache_time = now;
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+ }
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+ return ns_zoom_cached_enabled;
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+}
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+
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/* Scan overlay before-string / after-string properties in the
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selected window for a completion candidate with a "selected"
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face. Return the 0-based visual line index of the selected
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@@ -1215,11 +1240,23 @@ If a completion candidate is selected (overlay or child frame),
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static void
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ns_zoom_track_completion (struct frame *f, EmacsView *view)
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{
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- if (!UAZoomEnabled ())
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+ if (!ns_zoom_enabled_p ())
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return;
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if (!WINDOWP (f->selected_window))
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return;
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+ /* Rate-limit completion scan to 2 Hz. Completion overlays and
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+ child frames change at human interaction speed (<<10 Hz), so
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+ checking every 500 ms is indistinguishable from every frame
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+ while eliminating per-redisplay FOR_EACH_FRAME iteration. */
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+ {
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+ static CFAbsoluteTime last_completion_track;
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+ CFAbsoluteTime now = CFAbsoluteTimeGetCurrent ();
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+ if (now - last_completion_track < 0.5)
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+ return;
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+ last_completion_track = now;
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+ }
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+
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specpdl_ref count = SPECPDL_INDEX ();
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record_unwind_current_buffer ();
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@@ -1323,7 +1360,7 @@ so the visual offset is (ov_line + 1) * line_h from
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(zoomCursorUpdated is NO). */
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#if defined (MAC_OS_X_VERSION_MIN_REQUIRED) \
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&& MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
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- if (view && !view->zoomCursorUpdated && UAZoomEnabled ()
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+ if (view && !view->zoomCursorUpdated && ns_zoom_enabled_p ()
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&& !NSIsEmptyRect (view->lastCursorRect))
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{
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NSRect r = view->lastCursorRect;
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@@ -3500,7 +3537,7 @@ EmacsView pixels (AppKit, flipped, top-left origin)
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#if defined (MAC_OS_X_VERSION_MIN_REQUIRED) \
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&& MAC_OS_X_VERSION_MIN_REQUIRED >= 101000
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- if (UAZoomEnabled ())
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+ if (ns_zoom_enabled_p ())
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{
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NSRect windowRect = [view convertRect:r toView:nil];
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NSRect screenRect
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--
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2.43.0
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