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perf: use libxml2 patch for faster xpath context init (#3389)
**What problem is this PR intended to solve?** After chatting with @nwellnhof in #3378, he went ahead and made an performance-focused change upstream in libxml2/gnome@bf5fcf6e that I'm pulling in here to the vendored library. Benchmark comparing this PR against v1.17.x ("main"): Comparison: large: main: 3910.6 i/s large: patched: 3759.6 i/s - same-ish: difference falls within error Comparison: small: patched: 242901.7 i/s small: main: 127486.0 i/s - 1.91x slower We could get greater performance gains by re-using `XPathContext` objects, but only at the cost of a significant amount of additional complexity, since in order to properly support recursive XPath evaluation, Nokogiri would have to push and pop "stack frames" containing: - internal state contextSize and proximityPosition - registered namespaces - registered variables - function lookup handler That feels like a lot of code for a small win. Comparatively, pulling in this upstream patch is still a ~2x speedup with zero additional complexity. That's a win. **Have you included adequate test coverage?** N/A **Does this change affect the behavior of either the C or the Java implementations?** Performance improvement impacting CRuby only.
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patches/libxml2/0019-xpath-Use-separate-static-hash-table-for-standard-fu.patch
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,244 @@ | ||
| From d3e3526111097560cf7c002613e2cb1d469b59e0 Mon Sep 17 00:00:00 2001 | ||
| From: Nick Wellnhofer <[email protected]> | ||
| Date: Sat, 21 Dec 2024 16:03:46 +0100 | ||
| Subject: [PATCH] xpath: Use separate static hash table for standard functions | ||
|
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| This avoids registering standard functions when creating an XPath | ||
| context. | ||
|
|
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| Lookup of extension functions is a bit slower now, but ultimately, all | ||
| function lookups should be moved to the compilation phase. | ||
|
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| (cherry picked from commit bf5fcf6e646bb51a0f6a3655a1d64bea97274867) | ||
| --- | ||
| xpath.c | 170 ++++++++++++++++++++++++++++++++------------------------ | ||
| 1 file changed, 98 insertions(+), 72 deletions(-) | ||
|
|
||
| diff --git a/xpath.c b/xpath.c | ||
| index 485d7747..21711653 100644 | ||
| --- a/xpath.c | ||
| +++ b/xpath.c | ||
| @@ -136,11 +136,48 @@ | ||
|
|
||
| #if defined(LIBXML_XPATH_ENABLED) || defined(LIBXML_SCHEMAS_ENABLED) | ||
|
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||
| -/************************************************************************ | ||
| - * * | ||
| - * Floating point stuff * | ||
| - * * | ||
| - ************************************************************************/ | ||
| +static void | ||
| +xmlXPathNameFunction(xmlXPathParserContextPtr ctxt, int nargs); | ||
| + | ||
| +static const struct { | ||
| + const char *name; | ||
| + xmlXPathFunction func; | ||
| +} xmlXPathStandardFunctions[] = { | ||
| + { "boolean", xmlXPathBooleanFunction }, | ||
| + { "ceiling", xmlXPathCeilingFunction }, | ||
| + { "count", xmlXPathCountFunction }, | ||
| + { "concat", xmlXPathConcatFunction }, | ||
| + { "contains", xmlXPathContainsFunction }, | ||
| + { "id", xmlXPathIdFunction }, | ||
| + { "false", xmlXPathFalseFunction }, | ||
| + { "floor", xmlXPathFloorFunction }, | ||
| + { "last", xmlXPathLastFunction }, | ||
| + { "lang", xmlXPathLangFunction }, | ||
| + { "local-name", xmlXPathLocalNameFunction }, | ||
| + { "not", xmlXPathNotFunction }, | ||
| + { "name", xmlXPathNameFunction }, | ||
| + { "namespace-uri", xmlXPathNamespaceURIFunction }, | ||
| + { "normalize-space", xmlXPathNormalizeFunction }, | ||
| + { "number", xmlXPathNumberFunction }, | ||
| + { "position", xmlXPathPositionFunction }, | ||
| + { "round", xmlXPathRoundFunction }, | ||
| + { "string", xmlXPathStringFunction }, | ||
| + { "string-length", xmlXPathStringLengthFunction }, | ||
| + { "starts-with", xmlXPathStartsWithFunction }, | ||
| + { "substring", xmlXPathSubstringFunction }, | ||
| + { "substring-before", xmlXPathSubstringBeforeFunction }, | ||
| + { "substring-after", xmlXPathSubstringAfterFunction }, | ||
| + { "sum", xmlXPathSumFunction }, | ||
| + { "true", xmlXPathTrueFunction }, | ||
| + { "translate", xmlXPathTranslateFunction } | ||
| +}; | ||
| + | ||
| +#define NUM_STANDARD_FUNCTIONS \ | ||
| + (sizeof(xmlXPathStandardFunctions) / sizeof(xmlXPathStandardFunctions[0])) | ||
| + | ||
| +#define SF_HASH_SIZE 64 | ||
| + | ||
| +static unsigned char xmlXPathSFHash[SF_HASH_SIZE]; | ||
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||
| double xmlXPathNAN = 0.0; | ||
| double xmlXPathPINF = 0.0; | ||
| @@ -156,6 +193,18 @@ xmlXPathInit(void) { | ||
| xmlInitParser(); | ||
| } | ||
|
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||
| +ATTRIBUTE_NO_SANITIZE_INTEGER | ||
| +static unsigned | ||
| +xmlXPathSFComputeHash(const xmlChar *name) { | ||
| + unsigned hashValue = 5381; | ||
| + const xmlChar *ptr; | ||
| + | ||
| + for (ptr = name; *ptr; ptr++) | ||
| + hashValue = hashValue * 33 + *ptr; | ||
| + | ||
| + return(hashValue); | ||
| +} | ||
| + | ||
| /** | ||
| * xmlInitXPathInternal: | ||
| * | ||
| @@ -164,6 +213,8 @@ xmlXPathInit(void) { | ||
| ATTRIBUTE_NO_SANITIZE("float-divide-by-zero") | ||
| void | ||
| xmlInitXPathInternal(void) { | ||
| + size_t i; | ||
| + | ||
| #if defined(NAN) && defined(INFINITY) | ||
| xmlXPathNAN = NAN; | ||
| xmlXPathPINF = INFINITY; | ||
| @@ -175,8 +226,34 @@ xmlInitXPathInternal(void) { | ||
| xmlXPathPINF = 1.0 / zero; | ||
| xmlXPathNINF = -xmlXPathPINF; | ||
| #endif | ||
| + | ||
| + /* | ||
| + * Initialize hash table for standard functions | ||
| + */ | ||
| + | ||
| + for (i = 0; i < SF_HASH_SIZE; i++) | ||
| + xmlXPathSFHash[i] = UCHAR_MAX; | ||
| + | ||
| + for (i = 0; i < NUM_STANDARD_FUNCTIONS; i++) { | ||
| + const char *name = xmlXPathStandardFunctions[i].name; | ||
| + int bucketIndex = xmlXPathSFComputeHash(BAD_CAST name) % SF_HASH_SIZE; | ||
| + | ||
| + while (xmlXPathSFHash[bucketIndex] != UCHAR_MAX) { | ||
| + bucketIndex += 1; | ||
| + if (bucketIndex >= SF_HASH_SIZE) | ||
| + bucketIndex = 0; | ||
| + } | ||
| + | ||
| + xmlXPathSFHash[bucketIndex] = i; | ||
| + } | ||
| } | ||
|
|
||
| +/************************************************************************ | ||
| + * * | ||
| + * Floating point stuff * | ||
| + * * | ||
| + ************************************************************************/ | ||
| + | ||
| /** | ||
| * xmlXPathIsNaN: | ||
| * @val: a double value | ||
| @@ -3979,18 +4056,6 @@ xmlXPathRegisterFuncLookup (xmlXPathContextPtr ctxt, | ||
| */ | ||
| xmlXPathFunction | ||
| xmlXPathFunctionLookup(xmlXPathContextPtr ctxt, const xmlChar *name) { | ||
| - if (ctxt == NULL) | ||
| - return (NULL); | ||
| - | ||
| - if (ctxt->funcLookupFunc != NULL) { | ||
| - xmlXPathFunction ret; | ||
| - xmlXPathFuncLookupFunc f; | ||
| - | ||
| - f = ctxt->funcLookupFunc; | ||
| - ret = f(ctxt->funcLookupData, name, NULL); | ||
| - if (ret != NULL) | ||
| - return(ret); | ||
| - } | ||
| return(xmlXPathFunctionLookupNS(ctxt, name, NULL)); | ||
| } | ||
|
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| @@ -4015,6 +4080,22 @@ xmlXPathFunctionLookupNS(xmlXPathContextPtr ctxt, const xmlChar *name, | ||
| if (name == NULL) | ||
| return(NULL); | ||
|
|
||
| + if (ns_uri == NULL) { | ||
| + int bucketIndex = xmlXPathSFComputeHash(name) % SF_HASH_SIZE; | ||
| + | ||
| + while (xmlXPathSFHash[bucketIndex] != UCHAR_MAX) { | ||
| + int funcIndex = xmlXPathSFHash[bucketIndex]; | ||
| + | ||
| + if (strcmp(xmlXPathStandardFunctions[funcIndex].name, | ||
| + (char *) name) == 0) | ||
| + return(xmlXPathStandardFunctions[funcIndex].func); | ||
| + | ||
| + bucketIndex += 1; | ||
| + if (bucketIndex >= SF_HASH_SIZE) | ||
| + bucketIndex = 0; | ||
| + } | ||
| + } | ||
| + | ||
| if (ctxt->funcLookupFunc != NULL) { | ||
| xmlXPathFuncLookupFunc f; | ||
|
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||
| @@ -13494,61 +13575,6 @@ xmlXPathEscapeUriFunction(xmlXPathParserContextPtr ctxt, int nargs) { | ||
| void | ||
| xmlXPathRegisterAllFunctions(xmlXPathContextPtr ctxt) | ||
| { | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"boolean", | ||
| - xmlXPathBooleanFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"ceiling", | ||
| - xmlXPathCeilingFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"count", | ||
| - xmlXPathCountFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"concat", | ||
| - xmlXPathConcatFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"contains", | ||
| - xmlXPathContainsFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"id", | ||
| - xmlXPathIdFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"false", | ||
| - xmlXPathFalseFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"floor", | ||
| - xmlXPathFloorFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"last", | ||
| - xmlXPathLastFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"lang", | ||
| - xmlXPathLangFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"local-name", | ||
| - xmlXPathLocalNameFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"not", | ||
| - xmlXPathNotFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"name", | ||
| - xmlXPathNameFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"namespace-uri", | ||
| - xmlXPathNamespaceURIFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"normalize-space", | ||
| - xmlXPathNormalizeFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"number", | ||
| - xmlXPathNumberFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"position", | ||
| - xmlXPathPositionFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"round", | ||
| - xmlXPathRoundFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"string", | ||
| - xmlXPathStringFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"string-length", | ||
| - xmlXPathStringLengthFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"starts-with", | ||
| - xmlXPathStartsWithFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"substring", | ||
| - xmlXPathSubstringFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"substring-before", | ||
| - xmlXPathSubstringBeforeFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"substring-after", | ||
| - xmlXPathSubstringAfterFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"sum", | ||
| - xmlXPathSumFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"true", | ||
| - xmlXPathTrueFunction); | ||
| - xmlXPathRegisterFunc(ctxt, (const xmlChar *)"translate", | ||
| - xmlXPathTranslateFunction); | ||
| - | ||
| xmlXPathRegisterFuncNS(ctxt, (const xmlChar *)"escape-uri", | ||
| (const xmlChar *)"http://www.w3.org/2002/08/xquery-functions", | ||
| xmlXPathEscapeUriFunction); | ||
| -- | ||
| 2.47.1 | ||
|
|
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