Hi Darrick,
Thank you very much for your very detailed review, I will fix them
one by one and send a V2 sooner.
// Robert
On 07/23/2013 01:30 AM, Darrick J. Wong wrote:
On Sun, Jul 21, 2013 at 10:38:12AM +0800, Robert Yang wrote:
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.
Well in that case I'll review harder. :)
(Actually I thought of a few more things this morning.)
// 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@xxxxxxxxxxxxx>
Acked-by: Darren Hart <dvhart@xxxxxxxxxxxxxxx>
---
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];
I wonder, do we allow variable length arrays? I recall Ted was trying to get
rid of these.
...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;
I suspect that calloc()ing a zero buffer and calling memcmp() would be faster
than a byte-for-byte comparison.
+ 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;
I think the entire make_holes clause could be lifted out of the inner while and
placed in the outer while, since the is-zero-buffer test depends only on the
input.
You could use FIEMAP/FIBMAP or SEEK_DATA or something to efficiently walk the
allocated regions of the incoming file. If they're available...
+ }
+ }
+ /* Normal copy */
+ if (got > 0) {
Then you don't need the test here.
+ *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) {
Well, that's one way to detect a sparse file coming in -- but do we care about
the case of copying in a non-sparse file that contains a lot of zero regions?
Maybe we could add a flag to the 'write' command to force make_holes=1?
(Or just figure it out ourselves via fiemap as suggested above.)
+ 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.
I don't think removing the extents flag is necessary; "touch /mnt/emptyfile"
creates an empty flag with the extents flag set.
--D
+ */
+ 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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