bryancall commented on code in PR #13670: URL: https://github.com/apache/trafficserver/pull/13670#discussion_r3997489398
########## tools/benchmark/benchmark_Regex.cc: ########## @@ -0,0 +1,512 @@ +/** @file + + Benchmarks for the tsutil Regex wrapper: time per operation and the number and size + of heap allocations each operation makes. + + The allocation half matters as much as the timing half. PCRE2 routes every allocation + it makes for a compile or a match through the callbacks the wrapper installs, and those + call the system allocator, so counting calls to malloc across a region counts exactly + what the wrapper caused. Under the just-in-time engine a match should reach the system + allocator zero times; the interpreter allocates a frames vector and does not. + + Interposing malloc is only wired up on Linux, where defining these symbols in the + executable is enough. Elsewhere the counters stay at zero and the report says so, so a + run on another platform still gives timings without quietly reporting zero allocations + as a result. + + @section license License + + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + */ + +#include <cstdio> +#include <cstdlib> +#include <cstring> +#include <string> +#include <string_view> +#include <vector> + +#define CATCH_CONFIG_ENABLE_BENCHMARKING +#include <catch2/catch_test_macros.hpp> +#include <catch2/benchmark/catch_benchmark.hpp> + +#include "tsutil/Regex.h" + +// --------------------------------------------------------------------------- +// Allocation counting +// --------------------------------------------------------------------------- + +namespace +{ +struct AllocStats { + unsigned long calls = 0; + unsigned long bytes = 0; +}; + +// Counting is per thread so a benchmark that spawns threads does not race the counters. +// These benchmarks are single threaded; the qualifier is here so the numbers stay honest +// if one is added later. +thread_local AllocStats alloc_stats; +thread_local bool alloc_counting = false; + +class CountAllocations +{ +public: + CountAllocations() + { + alloc_stats = AllocStats{}; + alloc_counting = true; + } + ~CountAllocations() { alloc_counting = false; } + + AllocStats + stats() const + { + return alloc_stats; + } +}; + +#if defined(__linux__) +constexpr bool ALLOC_COUNTING_AVAILABLE = true; +#else +constexpr bool ALLOC_COUNTING_AVAILABLE = false; +#endif + +} // namespace + +#if defined(__linux__) +#include <dlfcn.h> + +// Interpose the system allocator. Defining these in the executable takes precedence over +// libc for every caller in the process, which is what makes the count cover PCRE2's own +// allocations as well as the wrapper's. +namespace +{ +using malloc_fn = void *(*)(size_t); +using free_fn = void (*)(void *); +using calloc_fn = void *(*)(size_t, size_t); +using realloc_fn = void *(*)(void *, size_t); + +malloc_fn real_malloc = nullptr; +free_fn real_free = nullptr; +calloc_fn real_calloc = nullptr; +realloc_fn real_realloc = nullptr; + +// dlsym() itself can allocate while the real pointers are still being resolved. Hand +// those few allocations out of a static buffer rather than recursing. +alignas(std::max_align_t) char bootstrap_buffer[16384]; +size_t bootstrap_used = 0; +bool resolving = false; + +bool +from_bootstrap(void *p) +{ + return p >= static_cast<void *>(bootstrap_buffer) && p < static_cast<void *>(bootstrap_buffer + sizeof(bootstrap_buffer)); +} + +void * +bootstrap_alloc(size_t size) +{ + size_t const aligned = (size + alignof(std::max_align_t) - 1) & ~(alignof(std::max_align_t) - 1); + if (bootstrap_used + aligned > sizeof(bootstrap_buffer)) { + return nullptr; + } + void *p = bootstrap_buffer + bootstrap_used; + bootstrap_used += aligned; + return p; +} + +void +resolve_real_allocators() +{ + if (real_malloc != nullptr || resolving) { + return; + } + resolving = true; + real_malloc = reinterpret_cast<malloc_fn>(dlsym(RTLD_NEXT, "malloc")); + real_free = reinterpret_cast<free_fn>(dlsym(RTLD_NEXT, "free")); + real_calloc = reinterpret_cast<calloc_fn>(dlsym(RTLD_NEXT, "calloc")); + real_realloc = reinterpret_cast<realloc_fn>(dlsym(RTLD_NEXT, "realloc")); Review Comment: Fixed in f70992eb6e. All four are resolved into locals and published together with real_malloc last, since that is the pointer the early return tests, so no wrapper can observe a half-resolved table. Each wrapper still checks its own pointer: free leaks rather than calling null while resolving, and realloc no longer hands a bootstrap pointer to the system allocator. _🤖 Addressed by [Claude Code](https://claude.com/claude-code)_ ########## tools/benchmark/benchmark_Regex.cc: ########## @@ -0,0 +1,553 @@ +/** @file + + Benchmarks for the tsutil Regex wrapper: time per operation and the number and size + of heap allocations each operation makes. + + The allocation half matters as much as the timing half. PCRE2 routes every allocation + it makes for a compile or a match through the callbacks the wrapper installs, and those + call the system allocator, so counting calls to malloc across a region counts exactly + what the wrapper caused. Under the just-in-time engine a match should reach the system + allocator zero times; the interpreter allocates a frames vector and does not. + + Interposing malloc is only wired up on Linux, where defining these symbols in the + executable is enough. Elsewhere the counters stay at zero and the report says so, so a + run on another platform still gives timings without quietly reporting zero allocations + as a result. + + @section license License + + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + */ + +#include <cstdio> +#include <cstdlib> +#include <cstring> +#include <string> +#include <string_view> +#include <vector> + +#define CATCH_CONFIG_ENABLE_BENCHMARKING +#include <catch2/catch_test_macros.hpp> +#include <catch2/benchmark/catch_benchmark.hpp> + +#include "tsutil/Regex.h" + +// --------------------------------------------------------------------------- +// Allocation counting +// --------------------------------------------------------------------------- + +namespace +{ +struct AllocStats { + unsigned long calls = 0; + unsigned long bytes = 0; +}; + +// Counting is per thread so a benchmark that spawns threads does not race the counters. +// These benchmarks are single threaded; the qualifier is here so the numbers stay honest +// if one is added later. +thread_local AllocStats alloc_stats; +thread_local bool alloc_counting = false; + +class CountAllocations +{ +public: + CountAllocations() + { + alloc_stats = AllocStats{}; + alloc_counting = true; + } + ~CountAllocations() { alloc_counting = false; } + + AllocStats + stats() const + { + return alloc_stats; + } +}; + +#if defined(__linux__) +constexpr bool ALLOC_COUNTING_AVAILABLE = true; +#else +constexpr bool ALLOC_COUNTING_AVAILABLE = false; +#endif + +} // namespace + +#if defined(__linux__) +#include <dlfcn.h> + +// Interpose the system allocator. Defining these in the executable takes precedence over +// libc for every caller in the process, which is what makes the count cover PCRE2's own +// allocations as well as the wrapper's. +namespace +{ +using malloc_fn = void *(*)(size_t); +using free_fn = void (*)(void *); +using calloc_fn = void *(*)(size_t, size_t); +using realloc_fn = void *(*)(void *, size_t); + +malloc_fn real_malloc = nullptr; +free_fn real_free = nullptr; +calloc_fn real_calloc = nullptr; +realloc_fn real_realloc = nullptr; + +// dlsym() itself can allocate while the real pointers are still being resolved. Hand +// those few allocations out of a static buffer rather than recursing. +alignas(std::max_align_t) char bootstrap_buffer[16384]; +size_t bootstrap_used = 0; +bool resolving = false; + +bool +from_bootstrap(void *p) +{ + return p >= static_cast<void *>(bootstrap_buffer) && p < static_cast<void *>(bootstrap_buffer + sizeof(bootstrap_buffer)); +} + +void * +bootstrap_alloc(size_t size) +{ + size_t const aligned = (size + alignof(std::max_align_t) - 1) & ~(alignof(std::max_align_t) - 1); + if (bootstrap_used + aligned > sizeof(bootstrap_buffer)) { + return nullptr; + } + void *p = bootstrap_buffer + bootstrap_used; + bootstrap_used += aligned; + return p; +} + +// Resolve all four into locals and publish them together, with real_malloc last. dlsym() +// may allocate or free while these lookups are in progress, which re-enters the wrappers +// below; they test their own pointer and fall back to the bootstrap path while it is still +// null, so no wrapper can reach a half-resolved table. +void +resolve_real_allocators() +{ + if (real_malloc != nullptr || resolving) { + return; + } + resolving = true; + + auto *m = reinterpret_cast<malloc_fn>(dlsym(RTLD_NEXT, "malloc")); + auto *f = reinterpret_cast<free_fn>(dlsym(RTLD_NEXT, "free")); + auto *c = reinterpret_cast<calloc_fn>(dlsym(RTLD_NEXT, "calloc")); + auto *r = reinterpret_cast<realloc_fn>(dlsym(RTLD_NEXT, "realloc")); + + real_free = f; + real_calloc = c; + real_realloc = r; + real_malloc = m; // published last: this is the pointer the early return above tests + + resolving = false; +} + +void +record(size_t size) +{ + if (alloc_counting) { + ++alloc_stats.calls; + alloc_stats.bytes += size; + } +} +} // namespace + +extern "C" void * +malloc(size_t size) +{ + if (real_malloc == nullptr) { + resolve_real_allocators(); + if (real_malloc == nullptr) { + return bootstrap_alloc(size); + } + } + record(size); + return real_malloc(size); +} + +extern "C" void +free(void *p) +{ + if (p == nullptr || from_bootstrap(p)) { + return; + } + if (real_free == nullptr) { + resolve_real_allocators(); + if (real_free == nullptr) { + // Still resolving, so there is nothing to free through. Leaking the few blocks the + // loader turns over during startup is better than calling through a null pointer. + return; + } + } + real_free(p); +} + +extern "C" void * +calloc(size_t n, size_t size) +{ + if (real_calloc == nullptr) { + resolve_real_allocators(); + if (real_calloc == nullptr) { + void *p = bootstrap_alloc(n * size); + if (p != nullptr) { + memset(p, 0, n * size); + } + return p; + } + } + record(n * size); + return real_calloc(n, size); +} + +extern "C" void * +realloc(void *p, size_t size) +{ + if (real_realloc == nullptr) { + resolve_real_allocators(); + } + + // A block handed out by bootstrap_alloc() is not one the system allocator knows, so it + // cannot be passed to the real realloc. Move it instead: the bootstrap sizes are tiny and + // this happens only while the loader is still resolving. + if (from_bootstrap(p)) { + if (real_malloc == nullptr) { + return bootstrap_alloc(size); Review Comment: Fixed in da6b2fb340. Bootstrap blocks now carry their size in a header one max_align_t wide, so realloc copies min(old, new) bytes on both paths, including the one where real_malloc is still null and the replacement also comes from the bootstrap buffer. You are right that this path mattered: the loader reallocs while resolving symbols, and returning uninitialised storage there fails the lookup in a way that is very hard to trace back here. _🤖 Addressed by [Claude Code](https://claude.com/claude-code)_ -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
