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MDL-40585 backup: cache XML parent paths

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For $this->groupedpaths, using a key is faster as there is
no need to do in_array searches.

Parent cache allows dirname calls to be substantially reduced.
2048 was chosen as a cache size as this class operates on chunks
of the restore at a time, 8k questions produces a parent cache of
about 500 paths and uses 300K of memory.  Scaling up to 2048 will
use about 1.2M of RAM for really large restores.  This is acceptable
for the 48% function call reduction and the 10% runtime improvement
seen.
This commit is contained in:
Russell Smith
2013-07-15 15:07:35 +10:00
parent f8e6e5bc30
commit f27cb59c36
1 changed files with 42 additions and 5 deletions
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backup/util/xml/parser/processors/grouped_parser_processor.class.php
+42 -5
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@@ -42,6 +42,18 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
protected $groupedpaths; // Paths we are requesting grouped
protected $currentdata; // Where we'll be acummulating data
/**
* Keep cache of parent directory paths for XML parsing.
* @var array
*/
protected $parentcache = array();
/**
* Remaining space for parent directory paths.
* @var integer
*/
protected $parentcacheavailablesize = 2048;
public function __construct(array $paths = array()) {
$this->groupedpaths = array();
@@ -65,7 +77,7 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
$a->child = $found;
throw new progressive_parser_exception('xml_grouped_child_found', $a);
}
$this->groupedpaths[] = $path;
$this->groupedpaths[$path] = true;
}
parent::add_path($path);
}
@@ -141,7 +153,7 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
}
protected function path_is_grouped($path) {
return in_array($path, $this->groupedpaths);
return isset($this->groupedpaths[$path]);
}
/**
@@ -150,16 +162,41 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
* false if not
*/
protected function grouped_parent_exists($path) {
$parentpath = progressive_parser::dirname($path);
$parentpath = $this->get_parent_path($path);
while ($parentpath != '/') {
if ($this->path_is_grouped($parentpath)) {
return $parentpath;
}
$parentpath = progressive_parser::dirname($parentpath);
$parentpath = $this->get_parent_path($parentpath);
}
return false;
}
/**
* Get the parent path using a local cache for performance.
*
* @param $path string The pathname you wish to obtain the parent name for.
* @return string The parent pathname.
*/
protected function get_parent_path($path) {
if (!isset($this->parentcache[$path])) {
$this->parentcache[$path] = progressive_parser::dirname($path);
$this->parentcacheavailablesize--;
if ($this->parentcacheavailablesize < 0) {
// Older first is cheaper than LRU. We use 10% as items are grouped together and the large quiz
// restore from MDL-40585 used only 600 parent paths. This is an XML heirarchy, so common paths
// are grouped near each other. eg; /question_bank/question_category/question/element. After keeping
// question_bank paths in the cache when we move to another area and the question_bank cache is not
// useful any longer.
$this->parentcache = array_slice($this->parentcache, 200, null, true);
$this->parentcacheavailablesize += 200;
}
}
return $this->parentcache[$path];
}
/**
* Function that will look for any grouped
* child for the given path, returning it if found,
@@ -167,7 +204,7 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
*/
protected function grouped_child_exists($path) {
$childpath = $path . '/';
foreach ($this->groupedpaths as $groupedpath) {
foreach ($this->groupedpaths as $groupedpath => $set) {
if (strpos($groupedpath, $childpath) === 0) {
return $groupedpath;
}