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

[Robert Yang <liezhi.yang@windriver.com>]

Hi Darrick,

Thanks for your reply, it seems that 64K is a good idea since put 128K
on the stack might cause problems, I will wait for one or two days for
more comments on other parts of the patches, then send a V2 with the
updates.

// Robert


On 07/20/2013 02:55 AM, Darrick J. Wong wrote:
> 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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