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[Emacs-diffs] master cf31645: * src/alloc.c: Avoid O(N²) complexity whe
From: |
Stefan Monnier |
Subject: |
[Emacs-diffs] master cf31645: * src/alloc.c: Avoid O(N²) complexity when unchaining markers (bug#24548). |
Date: |
Fri, 23 Mar 2018 11:10:00 -0400 (EDT) |
branch: master
commit cf3164523b32f01dbaad2c1364ecf2dcf8f22aa5
Author: Stefan Monnier <address@hidden>
Commit: Stefan Monnier <address@hidden>
* src/alloc.c: Avoid O(N²) complexity when unchaining markers (bug#24548).
Unchain all dead markers with a single scan of the markers list,
instead of calling the O(N) 'unchain_marker' N times.
(unchain_dead_markers): New function.
(sweep_buffers): Use it.
(gc_sweep): Sweep buffers before markers.
(sweep_misc): Check that markers have been unchained when reclaiming them.
---
src/alloc.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/src/alloc.c b/src/alloc.c
index da01173..5eaf7cb 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -7095,7 +7095,9 @@ sweep_misc (void)
if (!mblk->markers[i].m.u_any.gcmarkbit)
{
if (mblk->markers[i].m.u_any.type == Lisp_Misc_Marker)
- unchain_marker (&mblk->markers[i].m.u_marker);
+ /* Make sure markers have been unchained from their buffer
+ in sweep_buffer before we collect them. */
+ eassert (!mblk->markers[i].m.u_marker.buffer);
else if (mblk->markers[i].m.u_any.type == Lisp_Misc_Finalizer)
unchain_finalizer (&mblk->markers[i].m.u_finalizer);
#ifdef HAVE_MODULES
@@ -7142,6 +7144,23 @@ sweep_misc (void)
total_free_markers = num_free;
}
+/* Remove BUFFER's markers that are due to be swept. This is needed since
+ we treat BUF_MARKERS and markers's `next' field as weak pointers. */
+static void
+unchain_dead_markers (struct buffer *buffer)
+{
+ struct Lisp_Marker *this, **prev = &BUF_MARKERS (buffer);
+
+ while ((this = *prev))
+ if (this->gcmarkbit)
+ prev = &this->next;
+ else
+ {
+ this->buffer = NULL;
+ *prev = this->next;
+ }
+}
+
NO_INLINE /* For better stack traces */
static void
sweep_buffers (void)
@@ -7160,6 +7179,7 @@ sweep_buffers (void)
VECTOR_UNMARK (buffer);
/* Do not use buffer_(set|get)_intervals here. */
buffer->text->intervals = balance_intervals (buffer->text->intervals);
+ unchain_dead_markers (buffer);
total_buffers++;
bprev = &buffer->next;
}
@@ -7179,8 +7199,8 @@ gc_sweep (void)
sweep_floats ();
sweep_intervals ();
sweep_symbols ();
- sweep_misc ();
sweep_buffers ();
+ sweep_misc ();
sweep_vectors ();
check_string_bytes (!noninteractive);
}
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