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css: Add fast-path for parent selector matching

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Add a fast path for parent selector matching that uses a bloom filter to
quickly discard selectors that can't possibly match.

Keep in mind that we match using a bloom filter, so we might
accidentally include too many selectors when hash/bucket collisions
occur.
That's not a correctness problem though, because we'll do a real check
afterwards.

The idea for this change is taken from browsers, in particular WebKit.
This commit is contained in:
Benjamin Otte 2020-01-26 04:37:17 +01:00
parent 6aac56e144
commit 170130f1d9
14 changed files with 371 additions and 77 deletions
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158
gtk/gtkcountingbloomfilterprivate.h Normal file
View File

@ -0,0 +1,158 @@
/*
* Copyright © 2020 Benjamin Otte
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*
* Authors: Benjamin Otte <otte@gnome.org>
*/
#ifndef __GTK_COUNTING_BLOOM_FILTER_PRIVATE_H__
#define __GTK_COUNTING_BLOOM_FILTER_PRIVATE_H__
#include <glib.h>
G_BEGIN_DECLS
/*
* SECTION:gtkcountingbloomfilter
* @Short_description: A counting bloom filter
* @Title: GtkCountingBloomFilter
* @See_also: https://en.wikipedia.org/wiki/Bloom_filter,
* https://en.wikipedia.org/wiki/Counting_Bloom_filter
*
* This implements a counting bloom filter. A bloom filter is a space-efficient
* probabilistic data structure that is used to test whether an element may be
* a member of a set.
* The Wikipedia links provide a lot more details into how and why this data
* structure works and when to use it.
*
* This implementation is based on similar implementations in web browsers, because it's
* original use case is the same: Making CSS lookups fast.
*
* As such, the number of bits is hardcoded to 12 and the elements in the set
* are 16bit hash values.
* It is possible to use 32bit hash values or a different number of bits, should this
* be considered useful.
*/
/* The number of bits from the hash we care about */
#define GTK_COUNTING_BLOOM_FILTER_BITS (12)
/* The necessary size of the filter */
#define GTK_COUNTING_BLOOM_FILTER_SIZE (1 << GTK_COUNTING_BLOOM_FILTER_BITS)
typedef struct _GtkCountingBloomFilter GtkCountingBloomFilter;
struct _GtkCountingBloomFilter
{
guint8 buckets[GTK_COUNTING_BLOOM_FILTER_SIZE];
};
static inline void gtk_counting_bloom_filter_add (GtkCountingBloomFilter *self,
guint16 hash);
static inline void gtk_counting_bloom_filter_remove (GtkCountingBloomFilter *self,
guint16 hash);
static inline gboolean gtk_counting_bloom_filter_may_contain (const GtkCountingBloomFilter *self,
guint16 hash);
/*
* GTK_COUNTING_BLOOM_FILTER_INIT:
*
* Initialize the bloom filter. As bloom filters are always stack-allocated,
* initialization should happen when defining them, like:
* ```c
* GtkCountingBloomFilter filter = GTK_COUNTING_BLOOM_FILTER_INIT;
* ```
*
* The filter does not need to be freed.
*/
#define GTK_COUNTING_BLOOM_FILTER_INIT { 0, }
/*
* gtk_counting_bloom_filter_add:
* @self: a #GtkCountingBloomFilter
* @hash: a hash value to add to the filter
*
* Adds the hash value to the filter.
*
* If the same hash value gets added multiple times, it will
* be considered as contained in the hash until it has been
* removed as many times.
**/
static inline void
gtk_counting_bloom_filter_add (GtkCountingBloomFilter *self,
guint16 hash)
{
guint16 bucket = hash % GTK_COUNTING_BLOOM_FILTER_SIZE;
if (self->buckets[bucket] == 255)
return;
self->buckets[bucket]++;
}
/*
* gtk_counting_bloom_filter_remove:
* @self: a #GtkCountingBloomFilter
* @hash: a hash value to remove from the filter
*
* Removes a hash value from the filter that has previously
* been added via gtk_counting_bloom_filter_add().
**/
static inline void
gtk_counting_bloom_filter_remove (GtkCountingBloomFilter *self,
guint16 hash)
{
guint16 bucket = hash % GTK_COUNTING_BLOOM_FILTER_SIZE;
if (self->buckets[bucket] == 255)
return;
g_assert (self->buckets[bucket] > 0);
self->buckets[bucket]--;
}
/*
* gtk_counting_bloom_filter_may_contain:
* @self: a #GtkCountingBloomFilter
* @hash: the hash value to check
*
* Checks if @hash may be contained in @self.
*
* A return value of %FALSE means that @hash is definitely not part
* of @self.
*
* A return value of %TRUE means that @hash may or may not have been
* added to @self. In that case a different method must be used to
* confirm that @hash is indeed part of the set.
*
* Returns: %FALSE if @hash is not part of @self.
**/
static inline gboolean
gtk_counting_bloom_filter_may_contain (const GtkCountingBloomFilter *self,
guint16 hash)
{
guint16 bucket = hash % GTK_COUNTING_BLOOM_FILTER_SIZE;
return self->buckets[bucket] != 0;
}
G_END_DECLS
#endif /* __GTK_COUNTING_BLOOM_FILTER_PRIVATE_H_ */

35
gtk/gtkcssnode.c
View File

@ -355,6 +355,7 @@ store_in_global_parent_cache (GtkCssNode *node,
static GtkCssStyle *
gtk_css_node_create_style (GtkCssNode *cssnode,
const GtkCountingBloomFilter *filter,
GtkCssChange change)
{
const GtkCssNodeDeclaration *decl;
@ -380,6 +381,7 @@ gtk_css_node_create_style (GtkCssNode *cssnode,
}
style = gtk_css_static_style_new_compute (gtk_css_node_get_style_provider (cssnode),
filter,
cssnode,
style_change);
@ -412,6 +414,7 @@ gtk_css_style_needs_recreation (GtkCssStyle *style,
static GtkCssStyle *
gtk_css_node_real_update_style (GtkCssNode *cssnode,
const GtkCountingBloomFilter *filter,
GtkCssChange change,
gint64 timestamp,
GtkCssStyle *style)
@ -421,7 +424,7 @@ gtk_css_node_real_update_style (GtkCssNode *cssnode,
static_style = GTK_CSS_STYLE (gtk_css_style_get_static_style (style));
if (gtk_css_style_needs_recreation (static_style, change))
new_static_style = gtk_css_node_create_style (cssnode, change);
new_static_style = gtk_css_node_create_style (cssnode, filter, change);
else
new_static_style = g_object_ref (static_style);
@ -951,6 +954,7 @@ gtk_css_node_needs_new_style (GtkCssNode *cssnode)
static void
gtk_css_node_ensure_style (GtkCssNode *cssnode,
const GtkCountingBloomFilter *filter,
gint64 current_time)
{
gboolean style_changed;
@ -959,18 +963,19 @@ gtk_css_node_ensure_style (GtkCssNode *cssnode,
return;
if (cssnode->parent)
gtk_css_node_ensure_style (cssnode->parent, current_time);
gtk_css_node_ensure_style (cssnode->parent, filter, current_time);
if (cssnode->style_is_invalid)
{
GtkCssStyle *new_style;
if (cssnode->previous_sibling)
gtk_css_node_ensure_style (cssnode->previous_sibling, current_time);
gtk_css_node_ensure_style (cssnode->previous_sibling, filter, current_time);
g_clear_pointer (&cssnode->cache, gtk_css_node_style_cache_unref);
new_style = GTK_CSS_NODE_GET_CLASS (cssnode)->update_style (cssnode,
filter,
cssnode->pending_changes,
current_time,
cssnode->style);
@ -996,7 +1001,7 @@ gtk_css_node_get_style (GtkCssNode *cssnode)
{
gint64 timestamp = gtk_css_node_get_timestamp (cssnode);
gtk_css_node_ensure_style (cssnode, timestamp);
gtk_css_node_ensure_style (cssnode, NULL, timestamp);
}
return cssnode->style;
@ -1301,14 +1306,16 @@ gtk_css_node_invalidate (GtkCssNode *cssnode,
static void
gtk_css_node_validate_internal (GtkCssNode *cssnode,
GtkCountingBloomFilter *filter,
gint64 timestamp)
{
GtkCssNode *child;
gboolean bloomed = FALSE;
if (!cssnode->invalid)
return;
gtk_css_node_ensure_style (cssnode, timestamp);
gtk_css_node_ensure_style (cssnode, filter, timestamp);
/* need to set to FALSE then to TRUE here to make it chain up */
gtk_css_node_set_invalid (cssnode, FALSE);
@ -1321,20 +1328,32 @@ gtk_css_node_validate_internal (GtkCssNode *cssnode,
child;
child = gtk_css_node_get_next_sibling (child))
{
if (child->visible)
gtk_css_node_validate_internal (child, timestamp);
if (!child->visible)
continue;
if (!bloomed)
{
gtk_css_node_declaration_add_bloom_hashes (cssnode->decl, filter);
bloomed = TRUE;
}
gtk_css_node_validate_internal (child, filter, timestamp);
}
if (bloomed)
gtk_css_node_declaration_remove_bloom_hashes (cssnode->decl, filter);
}
void
gtk_css_node_validate (GtkCssNode *cssnode)
{
GtkCountingBloomFilter filter = GTK_COUNTING_BLOOM_FILTER_INIT;
gint64 timestamp;
gint64 before = g_get_monotonic_time ();
timestamp = gtk_css_node_get_timestamp (cssnode);
gtk_css_node_validate_internal (cssnode, timestamp);
gtk_css_node_validate_internal (cssnode, &filter, timestamp);
if (cssnode->parent == NULL)
{

34
gtk/gtkcssnodedeclaration.c
View File

@ -312,6 +312,40 @@ gtk_css_node_declaration_get_classes (const GtkCssNodeDeclaration *decl,
return decl->classes;
}
void
gtk_css_node_declaration_add_bloom_hashes (const GtkCssNodeDeclaration *decl,
GtkCountingBloomFilter *filter)
{
guint i;
if (decl->name)
gtk_counting_bloom_filter_add (filter, gtk_css_hash_name (decl->name));
if (decl->id)
gtk_counting_bloom_filter_add (filter, gtk_css_hash_id (decl->id));
for (i = 0; i < decl->n_classes; i++)
{
gtk_counting_bloom_filter_add (filter, gtk_css_hash_class (decl->classes[i]));
}
}
void
gtk_css_node_declaration_remove_bloom_hashes (const GtkCssNodeDeclaration *decl,
GtkCountingBloomFilter *filter)
{
guint i;
if (decl->name)
gtk_counting_bloom_filter_remove (filter, gtk_css_hash_name (decl->name));
if (decl->id)
gtk_counting_bloom_filter_remove (filter, gtk_css_hash_id (decl->id));
for (i = 0; i < decl->n_classes; i++)
{
gtk_counting_bloom_filter_remove (filter, gtk_css_hash_class (decl->classes[i]));
}
}
guint
gtk_css_node_declaration_hash (gconstpointer elem)
{

6
gtk/gtkcssnodedeclarationprivate.h
View File

@ -18,6 +18,7 @@
#ifndef __GTK_CSS_NODE_DECLARATION_PRIVATE_H__
#define __GTK_CSS_NODE_DECLARATION_PRIVATE_H__
#include "gtkcountingbloomfilterprivate.h"
#include "gtkcsstypesprivate.h"
#include "gtkenums.h"
@ -47,6 +48,11 @@ gboolean gtk_css_node_declaration_has_class (const G
const GQuark * gtk_css_node_declaration_get_classes (const GtkCssNodeDeclaration *decl,
guint *n_classes);
void gtk_css_node_declaration_add_bloom_hashes (const GtkCssNodeDeclaration *decl,
GtkCountingBloomFilter *filter);
void gtk_css_node_declaration_remove_bloom_hashes (const GtkCssNodeDeclaration *decl,
GtkCountingBloomFilter *filter);
guint gtk_css_node_declaration_hash (gconstpointer elem);
gboolean gtk_css_node_declaration_equal (gconstpointer elem1,
gconstpointer elem2);

2
gtk/gtkcssnodeprivate.h
View File

@ -18,6 +18,7 @@
#ifndef __GTK_CSS_NODE_PRIVATE_H__
#define __GTK_CSS_NODE_PRIVATE_H__
#include "gtkcountingbloomfilterprivate.h"
#include "gtkcssnodedeclarationprivate.h"
#include "gtkcssnodestylecacheprivate.h"
#include "gtkcssstylechangeprivate.h"
@ -81,6 +82,7 @@ struct _GtkCssNodeClass
/* get frame clock or NULL (only relevant for root node) */
GdkFrameClock * (* get_frame_clock) (GtkCssNode *cssnode);
GtkCssStyle * (* update_style) (GtkCssNode *cssnode,
const GtkCountingBloomFilter *filter,
GtkCssChange pending_changes,
gint64 timestamp,
GtkCssStyle *old_style);

3
gtk/gtkcssprovider.c
View File

@ -449,6 +449,7 @@ gtk_css_style_provider_get_keyframes (GtkStyleProvider *provider,
static void
gtk_css_style_provider_lookup (GtkStyleProvider *provider,
const GtkCountingBloomFilter *filter,
GtkCssNode *node,
GtkCssLookup *lookup,
GtkCssChange *change)
@ -463,7 +464,7 @@ gtk_css_style_provider_lookup (GtkStyleProvider *provider,
if (_gtk_css_selector_tree_is_empty (priv->tree))
return;
tree_rules = _gtk_css_selector_tree_match_all (priv->tree, node);
tree_rules = _gtk_css_selector_tree_match_all (priv->tree, filter, node);
if (tree_rules)
{
verify_tree_match_results (css_provider, node, tree_rules);

107
gtk/gtkcssselector.c
View File

@ -168,24 +168,6 @@ g_ptr_array_insert_sorted (GPtrArray *array,
g_ptr_array_insert (array, i, data);
}
static void
gtk_css_selector_tree_found_match (const GtkCssSelectorTree *tree,
GPtrArray **array)
{
int i;
gpointer *matches;
matches = gtk_css_selector_tree_get_matches (tree);
if (matches)
{
if (!*array)
*array = g_ptr_array_sized_new (16);
for (i = 0; matches[i] != NULL; i++)
g_ptr_array_insert_sorted (*array, matches[i]);
}
}
static inline gboolean
gtk_css_selector_match (const GtkCssSelector *selector,
GtkCssNode *node)
@ -1864,38 +1846,115 @@ gtk_css_selectors_skip_initial_selector (GtkCssSelector *selector, const GtkCssS
return (GtkCssSelector *)gtk_css_selector_previous (selector);
}
static gboolean
gtk_css_selector_tree_match_bloom (const GtkCssSelectorTree *tree,
const GtkCountingBloomFilter *filter,
gboolean skipping)
{
const GtkCssSelectorTree *prev;
switch (tree->selector.class->category)
{
case GTK_CSS_SELECTOR_CATEGORY_SIMPLE:
break;
case GTK_CSS_SELECTOR_CATEGORY_SIMPLE_RADICAL:
if (skipping)
break;
if (!gtk_counting_bloom_filter_may_contain (filter,
gtk_css_selector_hash_one (&tree->selector)))
return FALSE;
break;
case GTK_CSS_SELECTOR_CATEGORY_PARENT:
skipping = FALSE;
break;
case GTK_CSS_SELECTOR_CATEGORY_SIBLING:
skipping = TRUE;
break;
default:
g_assert_not_reached ();
return FALSE;
}
if (gtk_css_selector_tree_get_matches (tree))
return TRUE;
for (prev = gtk_css_selector_tree_get_previous (tree);
prev != NULL;
prev = gtk_css_selector_tree_get_sibling (prev))
{
if (gtk_css_selector_tree_match_bloom (prev, filter, skipping))
return TRUE;
}
return FALSE;
}
typedef struct
{
const GtkCountingBloomFilter *filter;
GPtrArray *results;
} TreeMatchData;
static void
gtk_css_selector_tree_found_match (const GtkCssSelectorTree *tree,
TreeMatchData *tm)
{
int i;
gpointer *matches;
matches = gtk_css_selector_tree_get_matches (tree);
if (matches)
{
if (tm->results == NULL)
tm->results = g_ptr_array_sized_new (16);
for (i = 0; matches[i] != NULL; i++)
g_ptr_array_insert_sorted (tm->results, matches[i]);
}
}
static gboolean
gtk_css_selector_tree_match_foreach (const GtkCssSelector *selector,
GtkCssNode *node,
gpointer res)
gpointer data)
{
TreeMatchData *tm = data;
const GtkCssSelectorTree *tree = (const GtkCssSelectorTree *) selector;
const GtkCssSelectorTree *prev;
if (!gtk_css_selector_match (selector, node))
return FALSE;
gtk_css_selector_tree_found_match (tree, res);
gtk_css_selector_tree_found_match (tree, tm);
if (tm->filter && !gtk_css_selector_is_simple (&tree->selector))
{
/* We can pass both TRUE or FALSE for skipping here, because the
* function will immediately update it. */
if (!gtk_css_selector_tree_match_bloom (tree, tm->filter, FALSE))
return FALSE;
}
for (prev = gtk_css_selector_tree_get_previous (tree);
prev != NULL;
prev = gtk_css_selector_tree_get_sibling (prev))
gtk_css_selector_foreach (&prev->selector, node, gtk_css_selector_tree_match_foreach, res);
gtk_css_selector_foreach (&prev->selector, node, gtk_css_selector_tree_match_foreach, tm);
return FALSE;
}
GPtrArray *
_gtk_css_selector_tree_match_all (const GtkCssSelectorTree *tree,
const GtkCountingBloomFilter *filter,
GtkCssNode *node)
{
GPtrArray *array = NULL;
TreeMatchData tm = { filter, NULL };
for (; tree != NULL;
tree = gtk_css_selector_tree_get_sibling (tree))
gtk_css_selector_foreach (&tree->selector, node, gtk_css_selector_tree_match_foreach, &array);
gtk_css_selector_foreach (&tree->selector, node, gtk_css_selector_tree_match_foreach, &tm);
return array;
return tm.results;
}
/* The code for collecting matches assumes that the name, id and classes

2
gtk/gtkcssselectorprivate.h
View File

@ -18,6 +18,7 @@
#ifndef __GTK_CSS_SELECTOR_PRIVATE_H__
#define __GTK_CSS_SELECTOR_PRIVATE_H__
#include "gtk/gtkcountingbloomfilterprivate.h"
#include "gtk/gtkcsstypesprivate.h"
#include "gtk/gtkcssparserprivate.h"
@ -42,6 +43,7 @@ int _gtk_css_selector_compare (const GtkCssSelector *a,
void _gtk_css_selector_tree_free (GtkCssSelectorTree *tree);
GPtrArray * _gtk_css_selector_tree_match_all (const GtkCssSelectorTree *tree,
const GtkCountingBloomFilter *filter,
GtkCssNode *node);
GtkCssChange _gtk_css_selector_tree_get_change_all (const GtkCssSelectorTree *tree,
GtkCssNode *node);

4
gtk/gtkcssstaticstyle.c
View File

@ -161,10 +161,12 @@ gtk_css_static_style_get_default (void)
*/
if (default_style == NULL)
{
GtkCountingBloomFilter filter = GTK_COUNTING_BLOOM_FILTER_INIT;
GtkSettings *settings;
settings = gtk_settings_get_default ();
default_style = gtk_css_static_style_new_compute (GTK_STYLE_PROVIDER (settings),
&filter,
NULL,
0);
g_object_set_data_full (G_OBJECT (settings), I_("gtk-default-style"),
@ -176,6 +178,7 @@ gtk_css_static_style_get_default (void)
GtkCssStyle *
gtk_css_static_style_new_compute (GtkStyleProvider *provider,
const GtkCountingBloomFilter *filter,
GtkCssNode *node,
GtkCssChange change)
{
@ -187,6 +190,7 @@ gtk_css_static_style_new_compute (GtkStyleProvider *provider,
if (node)
gtk_style_provider_lookup (provider,
filter,
node,
&lookup,
change == 0 ? &change : NULL);

3
gtk/gtkcssstaticstyleprivate.h
View File

@ -22,6 +22,8 @@
#include "gtk/gtkcssstyleprivate.h"
#include "gtk/gtkcountingbloomfilterprivate.h"
G_BEGIN_DECLS
#define GTK_TYPE_CSS_STATIC_STYLE (gtk_css_static_style_get_type ())
@ -52,6 +54,7 @@ GType gtk_css_static_style_get_type (void) G_GNUC_CO
GtkCssStyle * gtk_css_static_style_get_default (void);
GtkCssStyle * gtk_css_static_style_new_compute (GtkStyleProvider *provider,
const GtkCountingBloomFilter *filter,
GtkCssNode *node,
GtkCssChange change);

3
gtk/gtkcsstransientnode.c
View File

@ -24,12 +24,13 @@ G_DEFINE_TYPE (GtkCssTransientNode, gtk_css_transient_node, GTK_TYPE_CSS_NODE)
static GtkCssStyle *
gtk_css_transient_node_update_style (GtkCssNode *cssnode,
const GtkCountingBloomFilter *filter,
GtkCssChange change,
gint64 timestamp,
GtkCssStyle *style)
{
/* This should get rid of animations */
return GTK_CSS_NODE_CLASS (gtk_css_transient_node_parent_class)->update_style (cssnode, change, 0, style);
return GTK_CSS_NODE_CLASS (gtk_css_transient_node_parent_class)->update_style (cssnode, filter, change, 0, style);
}
static void

3
gtk/gtkstylecascade.c
View File

@ -180,6 +180,7 @@ gtk_style_cascade_get_keyframes (GtkStyleProvider *provider,
static void
gtk_style_cascade_lookup (GtkStyleProvider *provider,
const GtkCountingBloomFilter *filter,
GtkCssNode *node,
GtkCssLookup *lookup,
GtkCssChange *change)
@ -193,7 +194,7 @@ gtk_style_cascade_lookup (GtkStyleProvider *provider,
item;
item = gtk_style_cascade_iter_next (cascade, &iter))
{
gtk_style_provider_lookup (item, node, lookup,
gtk_style_provider_lookup (item, filter, node, lookup,
change ? &iter_change : NULL);
if (change)
*change |= iter_change;

3
gtk/gtkstyleprovider.c
View File

@ -93,6 +93,7 @@ gtk_style_provider_get_keyframes (GtkStyleProvider *provider,
void
gtk_style_provider_lookup (GtkStyleProvider *provider,
const GtkCountingBloomFilter *filter,
GtkCssNode *node,
GtkCssLookup *lookup,
GtkCssChange *out_change)
@ -111,7 +112,7 @@ gtk_style_provider_lookup (GtkStyleProvider *provider,
if (!iface->lookup)
return;
iface->lookup (provider, node, lookup, out_change);
iface->lookup (provider, filter, node, lookup, out_change);
}
void

3
gtk/gtkstyleproviderprivate.h
View File

@ -19,6 +19,7 @@
#define __GTK_STYLE_PROVIDER_PRIVATE_H__
#include <glib-object.h>
#include "gtk/gtkcountingbloomfilterprivate.h"
#include "gtk/gtkcsskeyframesprivate.h"
#include "gtk/gtkcsslookupprivate.h"
#include "gtk/gtkcssnodeprivate.h"
@ -42,6 +43,7 @@ struct _GtkStyleProviderInterface
const char *name);
int (* get_scale) (GtkStyleProvider *provider);
void (* lookup) (GtkStyleProvider *provider,
const GtkCountingBloomFilter *filter,
GtkCssNode *node,
GtkCssLookup *lookup,
GtkCssChange *out_change);
@ -59,6 +61,7 @@ GtkCssKeyframes * gtk_style_provider_get_keyframes (GtkStyleProvid
const char *name);
int gtk_style_provider_get_scale (GtkStyleProvider *provider);
void gtk_style_provider_lookup (GtkStyleProvider *provider,
const GtkCountingBloomFilter *filter,
GtkCssNode *node,
GtkCssLookup *lookup,
GtkCssChange *out_change);