mongodb/db/flushtest.cpp

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

// logstream defines these, we don't want that:
#undef cout
#undef endl

#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(10);
		}
		int ms = t.millis();
		cout << "flush with sleeps intermixed: " << ms << "ms, " << (ms-5000) / 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(10);
		}
		int ms = t.millis();
		cout << "fullsync with sleeps intermixed: " << ms << "ms, " << (ms-5000) / 500.0 << "ms/request" << endl;
	}
	}

	// with noatime
	{
		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;
	}
    
	return 0;
}