rocksdb/util/jemalloc_nodump_allocator.cc

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

#include "util/jemalloc_nodump_allocator.h"

#include <string>
#include <thread>

#include "port/likely.h"
#include "port/port.h"
#include "util/string_util.h"

namespace rocksdb {

#ifdef ROCKSDB_JEMALLOC_NODUMP_ALLOCATOR

std::atomic<extent_alloc_t*> JemallocNodumpAllocator::original_alloc_{nullptr};

JemallocNodumpAllocator::JemallocNodumpAllocator(
    std::unique_ptr<extent_hooks_t>&& arena_hooks, unsigned arena_index)
    : arena_hooks_(std::move(arena_hooks)),
      arena_index_(arena_index),
      tcache_(&JemallocNodumpAllocator::DestroyThreadSpecificCache) {}

int JemallocNodumpAllocator::GetThreadSpecificCache() {
  // We always enable tcache. The only corner case is when there are a ton of
  // threads accessing with low frequency, then it could consume a lot of
  // memory (may reach # threads * ~1MB) without bringing too much benefit.
  unsigned* tcache_index = reinterpret_cast<unsigned*>(tcache_.Get());
  if (UNLIKELY(tcache_index == nullptr)) {
    // Instantiate tcache.
    tcache_index = new unsigned(0);
    size_t tcache_index_size = sizeof(unsigned);
    int ret =
        mallctl("tcache.create", tcache_index, &tcache_index_size, nullptr, 0);
    if (ret != 0) {
      // No good way to expose the error. Silently disable tcache.
      delete tcache_index;
      return MALLOCX_TCACHE_NONE;
    }
    tcache_.Reset(static_cast<void*>(tcache_index));
  }
  return MALLOCX_TCACHE(*tcache_index);
}

void* JemallocNodumpAllocator::Allocate(size_t size) {
  int tcache_flag = GetThreadSpecificCache();
  return mallocx(size, MALLOCX_ARENA(arena_index_) | tcache_flag);
}

void JemallocNodumpAllocator::Deallocate(void* p) {
  // Obtain tcache.
  int tcache_flag = GetThreadSpecificCache();
  // No need to pass arena index to dallocx(). Jemalloc will find arena index
  // from its own metadata.
  dallocx(p, tcache_flag);
}

void* JemallocNodumpAllocator::Alloc(extent_hooks_t* extent, void* new_addr,
                                     size_t size, size_t alignment, bool* zero,
                                     bool* commit, unsigned arena_ind) {
  extent_alloc_t* original_alloc =
      original_alloc_.load(std::memory_order_relaxed);
  assert(original_alloc != nullptr);
  void* result = original_alloc(extent, new_addr, size, alignment, zero, commit,
                                arena_ind);
  if (result != nullptr) {
    int ret = madvise(result, size, MADV_DONTDUMP);
    if (ret != 0) {
      fprintf(
          stderr,
          "JemallocNodumpAllocator failed to set MADV_DONTDUMP, error code: %d",
          ret);
      assert(false);
    }
  }
  return result;
}

Status JemallocNodumpAllocator::DestroyArena(unsigned arena_index) {
  assert(arena_index != 0);
  std::string key = "arena." + ToString(arena_index) + ".destroy";
  int ret = mallctl(key.c_str(), nullptr, 0, nullptr, 0);
  if (ret != 0) {
    return Status::Incomplete("Failed to destroy jemalloc arena, error code: " +
                              ToString(ret));
  }
  return Status::OK();
}

void JemallocNodumpAllocator::DestroyThreadSpecificCache(void* ptr) {
  assert(ptr != nullptr);
  unsigned* tcache_index = static_cast<unsigned*>(ptr);
  size_t tcache_index_size = sizeof(unsigned);
  int ret __attribute__((__unused__)) =
      mallctl("tcache.destroy", nullptr, 0, tcache_index, tcache_index_size);
  // Silently ignore error.
  assert(ret == 0);
  delete tcache_index;
}

JemallocNodumpAllocator::~JemallocNodumpAllocator() {
  // Destroy tcache before destroying arena.
  autovector<void*> tcache_list;
  tcache_.Scrape(&tcache_list, nullptr);
  for (void* tcache_index : tcache_list) {
    DestroyThreadSpecificCache(tcache_index);
  }
  // Destroy arena. Silently ignore error.
  Status s __attribute__((__unused__)) = DestroyArena(arena_index_);
  assert(s.ok());
}

size_t JemallocNodumpAllocator::UsableSize(void* p,
                                           size_t /*allocation_size*/) const {
  return malloc_usable_size(static_cast<void*>(p));
}
#endif  // ROCKSDB_JEMALLOC_NODUMP_ALLOCATOR

Status NewJemallocNodumpAllocator(
    std::shared_ptr<MemoryAllocator>* memory_allocator) {
  *memory_allocator = nullptr;
#ifndef ROCKSDB_JEMALLOC_NODUMP_ALLOCATOR
  return Status::NotSupported(
      "JemallocNodumpAllocator only available with jemalloc version >= 5 "
      "and MADV_DONTDUMP is available.");
#else
  if (memory_allocator == nullptr) {
    return Status::InvalidArgument("memory_allocator must be non-null.");
  }

  // Create arena.
  unsigned arena_index = 0;
  size_t arena_index_size = sizeof(arena_index);
  int ret =
      mallctl("arenas.create", &arena_index, &arena_index_size, nullptr, 0);
  if (ret != 0) {
    return Status::Incomplete("Failed to create jemalloc arena, error code: " +
                              ToString(ret));
  }
  assert(arena_index != 0);

  // Read existing hooks.
  std::string key = "arena." + ToString(arena_index) + ".extent_hooks";
  extent_hooks_t* hooks;
  size_t hooks_size = sizeof(hooks);
  ret = mallctl(key.c_str(), &hooks, &hooks_size, nullptr, 0);
  if (ret != 0) {
    JemallocNodumpAllocator::DestroyArena(arena_index);
    return Status::Incomplete("Failed to read existing hooks, error code: " +
                              ToString(ret));
  }

  // Store existing alloc.
  extent_alloc_t* original_alloc = hooks->alloc;
  extent_alloc_t* expected = nullptr;
  bool success =
      JemallocNodumpAllocator::original_alloc_.compare_exchange_strong(
          expected, original_alloc);
  if (!success && original_alloc != expected) {
    JemallocNodumpAllocator::DestroyArena(arena_index);
    return Status::Incomplete("Original alloc conflict.");
  }

  // Set the custom hook.
  std::unique_ptr<extent_hooks_t> new_hooks(new extent_hooks_t(*hooks));
  new_hooks->alloc = &JemallocNodumpAllocator::Alloc;
  extent_hooks_t* hooks_ptr = new_hooks.get();
  ret = mallctl(key.c_str(), nullptr, nullptr, &hooks_ptr, sizeof(hooks_ptr));
  if (ret != 0) {
    JemallocNodumpAllocator::DestroyArena(arena_index);
    return Status::Incomplete("Failed to set custom hook, error code: " +
                              ToString(ret));
  }

  // Create cache allocator.
  memory_allocator->reset(
      new JemallocNodumpAllocator(std::move(new_hooks), arena_index));
  return Status::OK();
#endif  // ROCKSDB_JEMALLOC_NODUMP_ALLOCATOR
}

}  // namespace rocksdb