mongodb/db/flushtest.cpp

/*
 *    Copyright (C) 2010 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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 Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "pch.h"
#include <stdio.h>
#include "../util/goodies.h"
#include <fcntl.h>

namespace mongo {

#if defined(F_FULLFSYNC)
    void fullsync(int f) {
        fcntl( f, F_FULLFSYNC );
    }
#else
    void fullsync(int f) {
        fdatasync(f);
    }
#endif

    int main(int argc, char* argv[], char *envp[] ) {
        cout << "hello" << endl;

        FILE *f = fopen("/data/db/temptest", "a");

        if ( f == 0 ) {
            cout << "can't open file\n";
            return 1;
        }

        {
            Timer t;
            for ( int i = 0; i < 50000; i++ )
                fwrite("abc", 3, 1, f);
            cout << "small writes: " << t.millis() << "ms" << endl;
        }

        {
            Timer t;
            for ( int i = 0; i < 10000; i++ ) {
                fwrite("abc", 3, 1, f);
                fflush(f);
                fsync( fileno( f ) );
            }
            int ms = t.millis();
            cout << "flush: " << ms << "ms, " << ms / 10000.0 << "ms/request" << endl;
        }

        {
            Timer t;
            for ( int i = 0; i < 500; i++ ) {
                fwrite("abc", 3, 1, f);
                fflush(f);
                fsync( fileno( f ) );
                sleepmillis(2);
            }
            int ms = t.millis() - 500 * 2;
            cout << "flush with sleeps: " << ms << "ms, " << ms / 500.0 << "ms/request" << endl;
        }

        char buf[8192];
        for ( int pass = 0; pass < 2; pass++ ) {
            cout << "pass " << pass << endl;
            {
                Timer t;
                int n = 500;
                for ( int i = 0; i < n; i++ ) {
                    if ( pass == 0 )
                        fwrite("abc", 3, 1, f);
                    else
                        fwrite(buf, 8192, 1, f);
                    buf[0]++;
                    fflush(f);
                    fullsync(fileno(f));
                }
                int ms = t.millis();
                cout << "fullsync: " << ms << "ms, " << ms / ((double) n) << "ms/request" << endl;
            }

            {
                Timer t;
                for ( int i = 0; i < 500; i++ ) {
                    if ( pass == 0 )
                        fwrite("abc", 3, 1, f);
                    else
                        fwrite(buf, 8192, 1, f);
                    buf[0]++;
                    fflush(f);
                    fullsync(fileno(f));
                    sleepmillis(2);
                }
                int ms = t.millis() - 2 * 500;
                cout << "fullsync with sleeps: " << ms << "ms, " << ms / 500.0 << "ms/request" << endl;
            }
        }

        // without growing
        {
            fclose(f);
            /* try from beginning of the file, where we aren't appending and changing the file length,
               to see if this is faster as the directory entry then doesn't have to be flushed (if noatime in effect).
            */
            f = fopen("/data/db/temptest", "r+");
            Timer t;
            int n = 500;
            for ( int i = 0; i < n; i++ ) {
                fwrite("xyz", 3, 1, f);
                fflush(f);
                fullsync(fileno(f));
            }
            int ms = t.millis();
            cout << "fullsync without growing: " << ms << "ms, " << ms / ((double) n) << "ms/request" << endl;
        }

        // without growing, with delay
        {
            fclose(f);
            /* try from beginning of the file, where we aren't appending and changing the file length,
               to see if this is faster as the directory entry then doesn't have to be flushed (if noatime in effect).
            */
            f = fopen("/data/db/temptest", "r+");
            Timer t;
            int n = 500;
            for ( int i = 0; i < n; i++ ) {
                fwrite("xyz", 3, 1, f);
                fflush(f);
                fullsync(fileno(f));
                sleepmillis(2);
            }
            int ms = t.millis() - 2 * 500;
            cout << "fullsync without growing with sleeps: " << ms << "ms, " << ms / ((double) n) << "ms/request" << endl;
        }

        return 0;
    }

} // namespace mongo