LMDB seq vs random write

.c

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/time.h>

#include <lmdb.h>

const int64_t MAP_SIZE = 50LL << 30;
const int BATCH_SIZE = 100000;

static MDB_env *env;
static MDB_dbi dbi;

static double get_ts() {
	static struct timeval tv;
	gettimeofday(&tv, NULL);
	return tv.tv_sec + (double) tv.tv_usec / 1000000;
}

static void db_open(char *db_path) {
	int rc = mkdir(db_path, 0755);
	if (rc && errno != EEXIST) {
		perror("mkdir");
		exit(1);
	}

	MDB_txn *txn;
	int env_opt = MDB_NORDAHEAD | MDB_NOSYNC;

	rc = mdb_env_create(&env);
	rc = mdb_env_set_mapsize(env, MAP_SIZE);
	rc = mdb_env_open(env, db_path, env_opt, 0664);
	if (rc) {
		fprintf(stderr, "open error: %s\n", mdb_strerror(rc));
		exit(1);
	}

	rc = mdb_txn_begin(env, NULL, 0, &txn);
	rc = mdb_open(txn, NULL, 0, &dbi);
	rc = mdb_txn_commit(txn);

	fprintf(stderr, "DB opened\n");
}

static void db_close() {
	if (env) {
		mdb_env_close(env);
		env = NULL;
	}
}

static void run_bench(char *input) {
	MDB_txn *txn;
	MDB_cursor *mc;
	MDB_val mkey, mval;
	int rc;
	int flag = 0;

	mdb_txn_begin(env, NULL, 0, &txn);
	mdb_cursor_open(txn, dbi, &mc);

	FILE *fp = fopen(input, "r");

	int line_cnt = 0, put_cnt = 0, tx_cnt = 0;
	double ts = get_ts();

	char buf[100];
	uint8_t key[32];
	int value[2];
	char *line;
	do {
		line = fgets(buf, 100, fp);
		if (line != NULL) {
			line_cnt++;

			// Skip @\0*7
			char *p = line + 8;
			int i, j, len = 64;
			for (i = 0, j = 0; j < len; i++, j += 2) {
				sscanf(p + j, "%02x", key + i);
			}
			sscanf(p + len, "->%d,%d", &value[0], &value[1]);

			mkey.mv_data = &key;
			mkey.mv_size = 32;
			mval.mv_data = &value;
			mval.mv_size = sizeof(value);
		
			rc = mdb_cursor_put(mc, &mkey, &mval, flag);
			if (rc) {
				fprintf(stderr, "put error: %s\n", mdb_strerror(rc));
				exit(0);
			}
			put_cnt++;
		} 
		if (line_cnt % 100000 == 0) {
			double new_ts = get_ts();
			double elapsed = new_ts - ts;
			
			double put_rate = put_cnt / elapsed;

			fprintf(stderr, "Read %d lines in %.2f seconds, %.2f puts/s\n", line_cnt, elapsed, put_rate);

			ts = new_ts;
			put_cnt = 0;
		}
		if (line_cnt % BATCH_SIZE == 0) {
			mdb_cursor_close(mc);
			mdb_txn_commit(txn);
			fprintf(stderr, "commit\n");
			mdb_txn_begin(env, NULL, 0, &txn);
			mdb_cursor_open(txn, dbi, &mc);
		}
	} while (line != NULL);

	fclose(fp);

	mdb_cursor_close(mc);
	mdb_txn_commit(txn);
}

int main(int argc, char **argv) {
	fprintf(stderr, "db_path: %s, input: %s\n", argv[1], argv[2]);
	db_open(argv[1]);
	run_bench(argv[2]);
	db_close();
	return 0;
}