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LevelDB now attempts to reuse the preceding MANIFEST and log file when re-opened.

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(Based on a suggestion by cmumford.)

"open" benchmark on my workstation speeds up significantly since we
can now avoid three fdatasync calls and a compaction per open:

  Before: ~80000 microseconds
  After:    ~130 microseconds

Details:

(1) Added Options::reuse_logs (currently defaults to false) to control
new behavior.  The intention is to change the default to true after some
baking.

(2) Added Env::NewAppendableFile() whose default implementation returns
a not-supported error.

(3) VersionSet::Recovery attempts to reuse the MANIFEST from which
it is recovering.

(4) DBImpl recovery attempts to reuse the last log file and memtable.

(5) db_test.cc now tests a new configuration that sets reuse_logs to true.

(6) fault_injection_test also tests a reuse_logs==true config.

(7) Added a new recovery_test.
This commit is contained in:
Sanjay Ghemawat
2014-12-11 08:13:18 -08:00
committed by Chris Mumford
parent 77948e7eec
commit ac1d69da31
22 changed files with 707 additions and 155 deletions
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7
db/db_bench.cc
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@@ -100,6 +100,9 @@ static int FLAGS_bloom_bits = -1;
// benchmark will fail.
static bool FLAGS_use_existing_db = false;
// If true, reuse existing log/MANIFEST files when re-opening a database.
static bool FLAGS_reuse_logs = false;
// Use the db with the following name.
static const char* FLAGS_db = NULL;
@@ -700,6 +703,7 @@ class Benchmark {
options.write_buffer_size = FLAGS_write_buffer_size;
options.max_open_files = FLAGS_open_files;
options.filter_policy = filter_policy_;
options.reuse_logs = FLAGS_reuse_logs;
Status s = DB::Open(options, FLAGS_db, &db_);
if (!s.ok()) {
fprintf(stderr, "open error: %s\n", s.ToString().c_str());
@@ -954,6 +958,9 @@ int main(int argc, char** argv) {
} else if (sscanf(argv[i], "--use_existing_db=%d%c", &n, &junk) == 1 &&
(n == 0 || n == 1)) {
FLAGS_use_existing_db = n;
} else if (sscanf(argv[i], "--reuse_logs=%d%c", &n, &junk) == 1 &&
(n == 0 || n == 1)) {
FLAGS_reuse_logs = n;
} else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
FLAGS_num = n;
} else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {