David Dabbs wrote:
most filenames are small. We have an optimization in reiser4 that assumes filenames are less than 15 characters, which most of them are.
-----Original Message----- From: Hans Reiser [mailto:[EMAIL PROTECTED] Sent: Saturday, August 07, 2004 11:18 PM To: David Dabbs Subject: Re: Was able to reproduce "cp: cannot stat file.x: Input/output error"
How about, code was X, now it is Y, with just the relevant parts of the
code cited?
Probably the most significant change to mongo sources is how it generates
file names. Mongo.pl had a hard coded value of 6 for the "max_fname"
parameter passed to reiser_fract_tree. I made this a parameter one can
specify on the mongo command line. I passed it a value of 23.
Maybe you should use a list of real filenames as well as a list of real directory names. You can reuse the filenames, so long as they are unique within a directory.
Hmm, it occurs to me that rather than using the 7 character filename prefix in the hash we should use first 4 letters and last 3 letters.
Nikita, zam, what do you think?
In addition, reiser_fract_tree.c now generates file names (not directories) with extensions. Before, every file name generated had none. Here is the original and modified code.
CODE WAS /* generate a unique filename */ void get_name_by_number(num_t this_files_number, char * str, char type) { double rnd; char t[16]; /* We need to generate filenames of different lengths */ rnd=rand(); rnd=rnd/RAND_MAX*max_fname+1; sprintf (t, "%%c%%0%ulu",(int) rnd ); sprintf (str, t, type, this_files_number);
}
NOW CODE IS
/* generate a unique filename */
void get_name_by_number(num_t this_files_number, char * str, char type)
{
double rnd;
char t[16];
/* We need to generate filenames of different lengths */
rnd=rand();
rnd=rnd/RAND_MAX*max_fname+1;
if( type == 'f' ) sprintf (t, "%%c%%0%ulu.%c",(int) rnd, '`'+(char)rnd );
else
sprintf (t, "%%c%%0%ulu",(int) rnd );
sprintf (str, t, type, this_files_number);
}
Backtick is the character immediately preceding 'a', so passing a value for max_fname that generates a character greater than 'z' might generate an extension character that might be a shell metacharacter. Hence my earlier warning about using this parameter.
Finally, I added two phases to mongo. MKDIRS and MKFILES. The first makes directories from a static list of directories cat-ted from a file. MKFILES does the same, except with files. The files are created by executing the following code taken directory from reiser_fract_tree:
/* make a file of a specified size */
void make_file(int size, char * fname)
{ char string [1025] = {0};
char * str = string;
int fd = 0;
int error;
static num_t this_files_number = 1;
/* open the file, and deal with the various errors that can occur */
if ((fd = open(fname, g_flags, 0666)) == -1 ) { if (errno == ENOSPC) { if (!already_whined) { printf("reiser-2021A: out of disk (or inodes) space, will keep trying\n"); already_whined = 1; /* we continue other file creation in out of space conditions */ } return; } /* it is sometimes useful to be able to run this program more than once inside the same directory, and that means skipping over filenames that already exist. Thus we ignore EEXIST, and pay attention to all else. */ if ( errno == EEXIST) { /* just skip existing file */ return; } perror ("open"); exit (errno); }
/* close the file */ if (close(fd)) { perror("close() failed"); exit(errno); } }
Since the above code simply opens and closes the file, every file created is zero length, and it creates _many_ zero-length files.
Why would you want that?
Before, all filesok. Unmounting between phases was probably a bad idea, as it benchmarks unmounting. It should be fixed.
created during a mongo run had some content, though I'd need to go back and
check the size distribution function to be sure.
Finally, there is the bit about mounting and unmounting. Mongo.pl first unmounts the target filesystem, then runs the proper mkfs command, mounted the filesystem, ran df to get the block usage, then unmounted the filesystem. To run each phase, mongo calls the function mongo_launcher, which mounted the filesystem, ran the command for N iterations, then unmounted the filesystem.
I made the following changes, see http://dabbs.net/reiser4/mongopl.html for more context.
In
init_fsys: don't unmount the filesystem after mkfs * df.
mongo_launcher: don't call &mount_fsys; at beginning and &umount_fsys; at end of each phase
Only umount_fsys at end of function mongo.
David
