rocksdb/db/malloc_stats.cc
Andrew Kryczka 0d57d93a06 Support jemalloc compiled with --with-jemalloc-prefix (#5521)
Summary:
Previously, if the jemalloc was built with nonempty string for
`--with-jemalloc-prefix`, then `HasJemalloc()` would return false on
Linux, so jemalloc would not be used at runtime. On Mac, it would cause
a linker failure due to no definitions found for the weak functions
declared in "port/jemalloc_helper.h". This should be a rare problem
because (1) on Linux the default `--with-jemalloc-prefix` value is the
empty string, and (2) Homebrew's build explicitly sets
`--with-jemalloc-prefix` to the empty string.

However, there are cases where `--with-jemalloc-prefix` is nonempty.
For example, when building jemalloc from source on Mac, the default
setting is `--with-jemalloc-prefix=je_`. Such jemalloc builds should be
usable by RocksDB.

The fix is simple. Defining `JEMALLOC_MANGLE` before including
"jemalloc.h" causes it to define unprefixed symbols that are aliases for
each of the prefixed symbols. Thanks to benesch for figuring this out
and explaining it to me.

Fixes https://github.com/facebook/rocksdb/issues/1462.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5521

Test Plan:
build jemalloc with prefixed symbols:

```
$ ./configure --with-jemalloc-prefix=lol
$ make
```

compile rocksdb against it:

```
$ WITH_JEMALLOC_FLAG=1 JEMALLOC=1 EXTRA_LDFLAGS="-L/home/andrew/jemalloc/lib/" EXTRA_CXXFLAGS="-I/home/andrew/jemalloc/include/" make -j12 ./db_bench
```

run db_bench and verify jemalloc actually used:

```
$ ./db_bench -benchmarks=fillrandom -statistics=true -dump_malloc_stats=true -stats_dump_period_sec=1
$ grep jemalloc /tmp/rocksdbtest-1000/dbbench/LOG
2019/06/29-12:20:52.088658 7fc5fb7f6700 [_impl/db_impl.cc:837] ___ Begin jemalloc statistics ___
...
```

Differential Revision: D16092758

fbshipit-source-id: c2c358346190ed62ceb2a3547a6c4c180b12f7c4
2019-07-02 12:07:01 -07:00

56 lines
1.6 KiB
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// 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).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "db/malloc_stats.h"
#ifndef ROCKSDB_LITE
#include <memory>
#include <string.h>
#include "port/jemalloc_helper.h"
namespace rocksdb {
#ifdef ROCKSDB_JEMALLOC
typedef struct {
char* cur;
char* end;
} MallocStatus;
static void GetJemallocStatus(void* mstat_arg, const char* status) {
MallocStatus* mstat = reinterpret_cast<MallocStatus*>(mstat_arg);
size_t status_len = status ? strlen(status) : 0;
size_t buf_size = (size_t)(mstat->end - mstat->cur);
if (!status_len || status_len > buf_size) {
return;
}
snprintf(mstat->cur, buf_size, "%s", status);
mstat->cur += status_len;
}
void DumpMallocStats(std::string* stats) {
if (!HasJemalloc()) {
return;
}
MallocStatus mstat;
const unsigned int kMallocStatusLen = 1000000;
std::unique_ptr<char[]> buf{new char[kMallocStatusLen + 1]};
mstat.cur = buf.get();
mstat.end = buf.get() + kMallocStatusLen;
malloc_stats_print(GetJemallocStatus, &mstat, "");
stats->append(buf.get());
}
#else
void DumpMallocStats(std::string*) {}
#endif // ROCKSDB_JEMALLOC
} // namespace rocksdb
#endif // !ROCKSDB_LITE