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* src/alloc.c: Avoid O(N²) complexity when unchaining markers (bug#24548).

Browse Source 
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.
This commit is contained in:
Stefan Monnier 2018-03-23 11:09:54 -04:00
parent 6695c1be51
commit cf3164523b
1 changed files with 22 additions and 2 deletions
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24
src/alloc.c
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@ -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);
}