db_bench can now disable flashcache for background threads

Summary: Most of the approach is copied from WebSQL's MySQL branch. It's nice that we can do this without touching core RocksDB code.

Test Plan: Compiles and runs. Didn't test flashback code, as I don't have flashback device and most if it is c/p

Reviewers: MarkCallaghan, sdong

Reviewed By: sdong

Subscribers: rven, lgalanis, kradhakrishnan, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D35391

HISTORY.md

@@ -1,5 +1,10 @@
 # Rocksdb Change Log
 
+## Unreleased
+
+### New Features
+* Added an experimental API for handling flashcache devices (blacklists background threads from caching their reads) -- NewFlashcacheAwareEnv
+
 ## 3.10.0 (3/24/2015)
 ### New Features
 * GetThreadStatus() is now able to report detailed thread status, including:

db/db_bench.cc

@@ -42,6 +42,7 @@ int main() {
 #include "rocksdb/filter_policy.h"
 #include "rocksdb/slice_transform.h"
 #include "rocksdb/perf_context.h"
+#include "rocksdb/utilities/flashcache.h"
 #include "port/port.h"
 #include "port/stack_trace.h"
 #include "util/crc32c.h"
@@ -531,6 +532,11 @@ DEFINE_string(compaction_fadvice, "NORMAL",
 static auto FLAGS_compaction_fadvice_e =
   rocksdb::Options().access_hint_on_compaction_start;
 
+DEFINE_bool(disable_flashcache_for_background_threads, false,
+            "Disable flashcache for background threads");
+
+DEFINE_string(flashcache_dev, "", "Path to flashcache device");
+
 DEFINE_bool(use_tailing_iterator, false,
             "Use tailing iterator to access a series of keys instead of get");
 DEFINE_int64(iter_refresh_interval_us, -1,
@@ -1680,6 +1686,8 @@ class Benchmark {
   }
 
  private:
+  std::unique_ptr<Env> flashcache_aware_env_;
+
   struct ThreadArg {
     Benchmark* bm;
     SharedState* shared;
@@ -1992,7 +2000,18 @@ class Benchmark {
       FLAGS_env->LowerThreadPoolIOPriority(Env::LOW);
       FLAGS_env->LowerThreadPoolIOPriority(Env::HIGH);
     }
-    options.env = FLAGS_env;
+    if (FLAGS_disable_flashcache_for_background_threads) {
+      flashcache_aware_env_ =
+          std::move(NewFlashcacheAwareEnv(FLAGS_env, FLAGS_flashcache_dev));
+      if (flashcache_aware_env_.get() == nullptr) {
+        fprintf(stderr, "Failed to open flashcahce device at %s\n",
+                FLAGS_flashcache_dev.c_str());
+        std::abort();
+      }
+      options.env = flashcache_aware_env_.get();
+    } else {
+      options.env = FLAGS_env;
+    }
     options.disableDataSync = FLAGS_disable_data_sync;
     options.use_fsync = FLAGS_use_fsync;
     options.wal_dir = FLAGS_wal_dir;

include/rocksdb/utilities/flashcache.h

@@ -0,0 +1,24 @@
+// Copyright (c) 2014, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#pragma once
+
+#include <string>
+#include "rocksdb/env.h"
+
+namespace rocksdb {
+
+// This API is experimental. We will mark it stable once we run it in production
+// for a while.
+// NewFlashcacheAwareEnv() creates and Env that blacklists all background
+// threads (used for flush and compaction) from using flashcache to cache their
+// reads. Reads from compaction thread don't need to be cached because they are
+// going to be soon made obsolete (due to nature of compaction)
+// Usually you would pass Env::Default() as base.
+// flashcache_dev is a path to the flashcache device
+extern std::unique_ptr<Env> NewFlashcacheAwareEnv(
+    Env* base, const std::string& flashcache_dev);
+
+}  // namespace rocksdb

src.mk

@@ -97,6 +97,7 @@ LIB_SOURCES =                                                   \
   utilities/document/document_db.cc                             \
   utilities/document/json_document_builder.cc                   \
   utilities/document/json_document.cc                           \
+  utilities/flashcache/flashcache.cc                            \
   utilities/geodb/geodb_impl.cc                                 \
   utilities/leveldb_options/leveldb_options.cc                  \
   utilities/merge_operators/put.cc                              \

third-party/flashcache/flashcache_ioctl.h

@@ -0,0 +1,55 @@
+/****************************************************************************
+ *  flashcache_ioctl.h
+ *  FlashCache: Device mapper target for block-level disk caching
+ *
+ *  Copyright 2010 Facebook, Inc.
+ *  Author: Mohan Srinivasan (mohan@facebook.com)
+ *
+ *  Based on DM-Cache:
+ *   Copyright (C) International Business Machines Corp., 2006
+ *   Author: Ming Zhao (mingzhao@ufl.edu)
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; under version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ ****************************************************************************/
+
+#ifdef OS_LINUX
+#ifndef FLASHCACHE_IOCTL_H
+#define FLASHCACHE_IOCTL_H
+
+#include <linux/types.h>
+
+#define FLASHCACHE_IOCTL 0xfe
+
+enum {
+	FLASHCACHEADDNCPID_CMD=200,
+	FLASHCACHEDELNCPID_CMD,
+	FLASHCACHEDELNCALL_CMD,
+	FLASHCACHEADDWHITELIST_CMD,
+	FLASHCACHEDELWHITELIST_CMD,
+	FLASHCACHEDELWHITELISTALL_CMD,
+};
+
+#define FLASHCACHEADDNCPID	_IOW(FLASHCACHE_IOCTL, FLASHCACHEADDNCPID_CMD, pid_t)
+#define FLASHCACHEDELNCPID	_IOW(FLASHCACHE_IOCTL, FLASHCACHEDELNCPID_CMD, pid_t)
+#define FLASHCACHEDELNCALL	_IOW(FLASHCACHE_IOCTL, FLASHCACHEDELNCALL_CMD, pid_t)
+
+#define FLASHCACHEADDBLACKLIST		FLASHCACHEADDNCPID
+#define FLASHCACHEDELBLACKLIST		FLASHCACHEDELNCPID
+#define FLASHCACHEDELALLBLACKLIST	FLASHCACHEDELNCALL
+
+#define FLASHCACHEADDWHITELIST		_IOW(FLASHCACHE_IOCTL, FLASHCACHEADDWHITELIST_CMD, pid_t)
+#define FLASHCACHEDELWHITELIST		_IOW(FLASHCACHE_IOCTL, FLASHCACHEDELWHITELIST_CMD, pid_t)
+#define FLASHCACHEDELALLWHITELIST	_IOW(FLASHCACHE_IOCTL, FLASHCACHEDELWHITELISTALL_CMD, pid_t)
+
+#endif /* FLASHCACHE_IOCTL_H */
+#endif /* OS_LINUX */

utilities/flashcache/flashcache.cc

@@ -0,0 +1,145 @@
+// Copyright (c) 2014, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#include "rocksdb/utilities/flashcache.h"
+
+#include "utilities/flashcache/flashcache.h"
+
+#ifdef OS_LINUX
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#include "third-party/flashcache/flashcache_ioctl.h"
+#endif
+
+namespace rocksdb {
+
+#if !defined(ROCKSDB_LITE) && defined(OS_LINUX)
+// Most of the code that handles flashcache is copied from websql's branch of
+// mysql-5.6
+class FlashcacheAwareEnv : public EnvWrapper {
+ public:
+  FlashcacheAwareEnv(Env* base, int cachedev_fd)
+      : EnvWrapper(base), cachedev_fd_(cachedev_fd) {
+    pid_t pid = getpid();
+    /* cleanup previous whitelistings */
+    if (ioctl(cachedev_fd_, FLASHCACHEDELALLWHITELIST, &pid) < 0) {
+      close(cachedev_fd_);
+      cachedev_fd_ = -1;
+      fprintf(stderr, "ioctl del-all-whitelist for flashcache failed\n");
+      return;
+    }
+    if (ioctl(cachedev_fd_, FLASHCACHEADDWHITELIST, &pid) < 0) {
+      fprintf(stderr, "ioctl add-whitelist for flashcache failed\n");
+    }
+  }
+
+  ~FlashcacheAwareEnv() {
+    // cachedev_fd_ is -1 if it's unitialized
+    if (cachedev_fd_ != -1) {
+      pid_t pid = getpid();
+      if (ioctl(cachedev_fd_, FLASHCACHEDELWHITELIST, &pid) < 0) {
+        fprintf(stderr, "ioctl del-whitelist for flashcache failed\n");
+      }
+      close(cachedev_fd_);
+    }
+  }
+
+  static int BlacklistCurrentThread(int cachedev_fd) {
+    pid_t pid = syscall(SYS_gettid);
+    return ioctl(cachedev_fd, FLASHCACHEADDNCPID, &pid);
+  }
+
+  static int WhitelistCurrentThread(int cachedev_fd) {
+    pid_t pid = syscall(SYS_gettid);
+    return ioctl(cachedev_fd, FLASHCACHEDELNCPID, &pid);
+  }
+
+  int GetFlashCacheFileDescriptor() { return cachedev_fd_; }
+
+  struct Arg {
+    Arg(void (*f)(void* arg), void* a, int _cachedev_fd)
+        : original_function_(f), original_arg_(a), cachedev_fd(_cachedev_fd) {}
+
+    void (*original_function_)(void* arg);
+    void* original_arg_;
+    int cachedev_fd;
+  };
+
+  static void BgThreadWrapper(void* a) {
+    Arg* arg = reinterpret_cast<Arg*>(a);
+    if (arg->cachedev_fd != -1) {
+      if (BlacklistCurrentThread(arg->cachedev_fd) < 0) {
+        fprintf(stderr, "ioctl add-nc-pid for flashcache failed\n");
+      }
+    }
+    arg->original_function_(arg->original_arg_);
+    if (arg->cachedev_fd != -1) {
+      if (WhitelistCurrentThread(arg->cachedev_fd) < 0) {
+        fprintf(stderr, "ioctl del-nc-pid for flashcache failed\n");
+      }
+    }
+    delete arg;
+  }
+
+  int UnSchedule(void* arg, Priority pri) override {
+    // no unschedule for you
+    return 0;
+  }
+
+  void Schedule(void (*f)(void* arg), void* a, Priority pri,
+                void* tag = nullptr) override {
+    EnvWrapper::Schedule(&BgThreadWrapper, new Arg(f, a, cachedev_fd_), pri,
+                         tag);
+  }
+
+ private:
+  int cachedev_fd_;
+};
+
+std::unique_ptr<Env> NewFlashcacheAwareEnv(Env* base,
+                                           const std::string& flashcache_dev) {
+  // Cachedev should remain open or ioctl will be lost
+  int cachedev_fd = open(flashcache_dev.c_str(), O_RDONLY);
+  if (cachedev_fd < 0) {
+    fprintf(stderr, "Open flash device failed\n");
+    return nullptr;
+  }
+
+  std::unique_ptr<Env> ret(new FlashcacheAwareEnv(base, cachedev_fd));
+  return std::move(ret);
+}
+
+int FlashcacheBlacklistCurrentThread(Env* flashcache_aware_env) {
+  int fd = dynamic_cast<FlashcacheAwareEnv*>(flashcache_aware_env)
+               ->GetFlashCacheFileDescriptor();
+  if (fd == -1) {
+    return -1;
+  }
+  return FlashcacheAwareEnv::BlacklistCurrentThread(fd);
+}
+int FlashcacheWhitelistCurrentThread(Env* flashcache_aware_env) {
+  int fd = dynamic_cast<FlashcacheAwareEnv*>(flashcache_aware_env)
+               ->GetFlashCacheFileDescriptor();
+  if (fd == -1) {
+    return -1;
+  }
+  return FlashcacheAwareEnv::WhitelistCurrentThread(fd);
+}
+
+#else   // !defined(ROCKSDB_LITE) && defined(OS_LINUX)
+std::unique_ptr<Env> NewFlashcacheAwareEnv(Env* base,
+                                           const std::string& flashcache_dev) {
+  return nullptr;
+}
+int FlashcacheBlacklistCurrentThread(Env* flashcache_aware_env) { return -1; }
+int FlashcacheWhitelistCurrentThread(Env* flashcache_aware_env) { return -1; }
+
+#endif  // !defined(ROCKSDB_LITE) && defined(OS_LINUX)
+
+}  // namespace rocksdb

utilities/flashcache/flashcache.h

@@ -0,0 +1,18 @@
+// Copyright (c) 2014, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#pragma once
+
+#include <string>
+#include "rocksdb/env.h"
+
+namespace rocksdb {
+
+// This is internal API that will make hacking on flashcache easier. Not sure if
+// we need to expose this to public users, probably not
+extern int FlashcacheBlacklistCurrentThread(Env* flashcache_aware_env);
+extern int FlashcacheWhitelistCurrentThread(Env* flashcache_aware_env);
+
+}  // namespace rocksdb