Re: [PATCH 2/2] debugfs.c: do sparse copy when src is a sparse file

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Jul 19, 2013 at 10:17:37AM +0800, Robert Yang wrote:
> Let debugfs do sparse copy when src is a sparse file, just like
> "cp --sparse=auto"
> 
> * For the
>   #define IO_BUFSIZE 32*1024
> 
>   This is from coreutils-8.13/src/ioblksize.h (GPL V3):
> /* As of Mar 2009, 32KiB is determined to be the minimium
>    blksize to best minimize system call overhead.
>    This can be tested with this script with the results
>    shown for a 1.7GHz pentium-m with 2GB of 400MHz DDR2 RAM:

Um.... GNU updated this to 64K a couple of years ago:
http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=blob;f=src/ioblksize.h;h=1ae93255e7d0ccf0855208c7ae5888209997bf16;hb=HEAD

Just for laughs I tried it on a T430 with an i5-3320M and 16G of DDR3-1600 RAM:

   1024=3.7 GB/s
   2048=7.1 GB/s
   4096=8.8 GB/s
   8192=14.9 GB/s
  16384=14.3 GB/s
  32768=13.4 GB/s
  65536=15.8 GB/s
 131072=20.7 GB/s
 262144=16.4 GB/s
 524288=15.9 GB/s
1048576=15.8 GB/s
2097152=15.1 GB/s
4194304=11.7 GB/s
8388608=9.9 GB/s
16777216=9.4 GB/s
33554432=9.3 GB/s
67108864=9.3 GB/s
134217728=8.8 GB/s

For that matter, a 2010-era i7-950/DDR3-1066 system showed this:

   1024=3.4 GB/s
   2048=5.6 GB/s
   4096=7.8 GB/s
   8192=9.5 GB/s
  16384=10.8 GB/s
  32768=11.4 GB/s
  65536=11.6 GB/s
 131072=12.2 GB/s
 262144=11.9 GB/s
 524288=12.3 GB/s
1048576=12.4 GB/s
2097152=12.5 GB/s
4194304=12.5 GB/s
8388608=10.3 GB/s
16777216=8.0 GB/s
33554432=7.6 GB/s
67108864=7.8 GB/s
134217728=7.5 GB/s

And for good measure, a cruddy old T2300 Core Duo from 2006 spat out this:

   1024=1.1 GB/s
   2048=2.1 GB/s
   4096=3.6 GB/s
   8192=5.0 GB/s
  16384=6.3 GB/s
  32768=6.5 GB/s
  65536=6.6 GB/s
 131072=7.0 GB/s
 262144=7.1 GB/s
 524288=7.1 GB/s
1048576=6.8 GB/s
2097152=4.4 GB/s
4194304=2.3 GB/s
8388608=2.0 GB/s
16777216=2.0 GB/s
33554432=2.0 GB/s
67108864=2.0 GB/s
134217728=1.9 GB/s

I suspect you could increase the buffer size to 128K (or possibly even BLKRAGET
size?) without much of a problem...

> 
>    for i in $(seq 0 10); do
>      size=$((8*1024**3)) #ensure this is big enough
>      bs=$((1024*2**$i))
>      printf "%7s=" $bs
>      dd bs=$bs if=/dev/zero of=/dev/null count=$(($size/$bs)) 2>&1 |
>      sed -n 's/.* \([0-9.]* [GM]B\/s\)/\1/p'
>    done
> 
>       1024=734 MB/s
>       2048=1.3 GB/s
>       4096=2.4 GB/s
>       8192=3.5 GB/s
>      16384=3.9 GB/s
>      32768=5.2 GB/s
>      65536=5.3 GB/s
>     131072=5.5 GB/s
>     262144=5.7 GB/s
>     524288=5.7 GB/s
>    1048576=5.8 GB/s
> 
>    Note that this is to minimize system call overhead.
>    Other values may be appropriate to minimize file system
>    or disk overhead.  For example on my current GNU/Linux system
>    the readahead setting is 128KiB which was read using:
> 
>    file="."
>    device=$(df -P --local "$file" | tail -n1 | cut -d' ' -f1)
>    echo $(( $(blockdev --getra $device) * 512 ))
> 
>    However there isn't a portable way to get the above.
>    In the future we could use the above method if available
>    and default to io_blksize() if not.
>  */
> enum { IO_BUFSIZE = 32*1024 };
> 
> Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
> Acked-by: Darren Hart <dvhart@linux.intel.com>
> ---
>  debugfs/debugfs.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 60 insertions(+), 10 deletions(-)
> 
> diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
> index b77d0b5..e443703 100644
> --- a/debugfs/debugfs.c
> +++ b/debugfs/debugfs.c
> @@ -37,6 +37,16 @@ extern char *optarg;
>  #include "../version.h"
>  #include "jfs_user.h"
>  
> +/* 32KiB is the minimium blksize to best minimize system call overhead. */
> +#ifndef IO_BUFSIZE
> +#define IO_BUFSIZE 32*1024
> +#endif
> +
> +/* Block size for `st_blocks' */
> +#ifndef S_BLKSIZE
> +#define S_BLKSIZE 512
> +#endif
> +
>  ss_request_table *extra_cmds;
>  const char *debug_prog_name;
>  int sci_idx;
> @@ -1571,14 +1581,17 @@ void do_find_free_inode(int argc, char *argv[])
>  }
>  
>  #ifndef READ_ONLY
> -static errcode_t copy_file(int fd, ext2_ino_t newfile)
> +static errcode_t copy_file(int fd, ext2_ino_t newfile, int bufsize,
> +			int make_holes, int *zero_written)
>  {
>  	ext2_file_t	e2_file;
>  	errcode_t	retval;
>  	int		got;
>  	unsigned int	written;
> -	char		buf[8192];
> +	char		buf[bufsize];

...well, I guess it could be more of a problem if you put 128K on the stack.

--D

>  	char		*ptr;
> +	char		*cp;
> +	int		count;
>  
>  	retval = ext2fs_file_open(current_fs, newfile,
>  				  EXT2_FILE_WRITE, &e2_file);
> @@ -1594,14 +1607,30 @@ static errcode_t copy_file(int fd, ext2_ino_t newfile)
>  			goto fail;
>  		}
>  		ptr = buf;
> +		cp = ptr;
> +		count = got;
>  		while (got > 0) {
> -			retval = ext2fs_file_write(e2_file, ptr,
> -						   got, &written);
> -			if (retval)
> -				goto fail;
> -
> -			got -= written;
> -			ptr += written;
> +			if (make_holes) {
> +				/* Check whether all is zero */
> +				while (count-- && *cp++ == 0)
> +					continue;
> +				if (count < 0) {
> +					 /* The whole block is zero, make a hole */
> +					retval = ext2fs_file_lseek(e2_file, got, EXT2_SEEK_CUR, NULL);
> +					if (retval)
> +						goto fail;
> +					got = 0;
> +				}
> +			}
> +			/* Normal copy */
> +			if (got > 0) {
> +				*zero_written = 0;
> +				retval = ext2fs_file_write(e2_file, ptr, got, &written);
> +				if (retval)
> +					goto fail;
> +				got -= written;
> +				ptr += written;
> +			}
>  		}
>  	}
>  	retval = ext2fs_file_close(e2_file);
> @@ -1620,6 +1649,9 @@ void do_write(int argc, char *argv[])
>  	ext2_ino_t	newfile;
>  	errcode_t	retval;
>  	struct ext2_inode inode;
> +	int		bufsize = IO_BUFSIZE;
> +	int		make_holes = 0;
> +	int 		zero_written = 1;
>  
>  	if (common_args_process(argc, argv, 3, 3, "write",
>  				"<native file> <new file>", CHECK_FS_RW))
> @@ -1684,9 +1716,27 @@ void do_write(int argc, char *argv[])
>  		return;
>  	}
>  	if (LINUX_S_ISREG(inode.i_mode)) {
> -		retval = copy_file(fd, newfile);
> +		if (statbuf.st_blocks < statbuf.st_size / S_BLKSIZE) {
> +			make_holes = 1;
> +			/*
> +			 * Use I/O blocksize as buffer size when
> +			 * copying sparse files.
> +			 */
> +			bufsize = statbuf.st_blksize;
> +		}
> +		retval = copy_file(fd, newfile, bufsize, make_holes, &zero_written);
>  		if (retval)
>  			com_err("copy_file", retval, 0);
> +
> +		if ((inode.i_flags & EXT4_EXTENTS_FL) && zero_written) {
> +			/*
> +			 * If no data is copied which indicateds that no write
> +			 * happens, we need to turn off the EXT4_EXTENTS_FL.
> +			 */
> +			inode.i_flags &= ~EXT4_EXTENTS_FL;
> +			if (debugfs_write_inode(newfile, &inode, argv[0]))
> +				close(fd);
> +		}
>  	}
>  	close(fd);
>  }
> -- 
> 1.8.1.2
> 
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