2015-10-20 17:56 GMT+03:00, Filipe Manana <fdman...@gmail.com>:
> On Tue, Oct 20, 2015 at 2:29 PM, Timofey Titovets <nefelim...@gmail.com>
> wrote:
>> For performance reason, leave data at the start of disk, is preferable
>> while deduping
>
> Have you made any performance tests to verify that?
pe, i don't run any performance test, at now
It's like defragmentation, can give a boost in specific cases, and if
assumption, what, beginning sectors of hdd, is faster
(this is true, because count of sectors is not equal, at the beginning
and end of hdd space)
And while, i not shall sure in my code, it's useless
>> It's might sense for the reasons:
>> 1. Spinning rust - start of the disk is much faster
>> 2. Btrfs can deallocate empty data chunk from the end of fs - ie it's
>> compact fs
>
> I don't see why that makes sense. First the clone/extent_same ioctls
> don't copy data, they just update metadata of the destination inode to
> point to the same extents as the source inode,
s true, but as i say before, data at the beggining, of hdd, can be
accessed faster, then data of the end of hdd
I.e. it's give a boost, after dedup, not while processing requests
>secondly, just because
> an offset of a file is lower the offset of the other file, it doesn't
> mean the physical (on disk) offset of the first file is lower than
> that of the other file...
Oh, so sad, then i must go deeper in the code -.-
>>
>> Signed-off-by: Timofey Titovets <nefelim...@gmail.com>
>> ---
>> fs/btrfs/ioctl.c | 9 +++++++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> index 3e3e613..3eb77c0 100644
>> --- a/fs/btrfs/ioctl.c
>> +++ b/fs/btrfs/ioctl.c
>> @@ -3074,8 +3074,13 @@ static int btrfs_extent_same(struct inode *src,
>> u64 loff, u64 olen,
>>
>> /* pass original length for comparison so we stay within i_size */
>> ret = btrfs_cmp_data(src, loff, dst, dst_loff, olen, &cmp);
>> - if (ret == 0)
>> - ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);
>> + if (ret == 0) {
>> + /* prefer inode with lowest offset as source for clone*/
>> + if (loff > dest_loff)
>> + ret = btrfs_clone(dst, src, dst_loff, olen, len, loff, 1);
>> + else
>> + ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);
>> + }
>>
>> if (same_inode)
>> unlock_extent(&BTRFS_I(src)->io_tree, same_lock_start,
>> --
>> 2.6.1
>
>
>
> --
> Filipe David Manana,
>
> "Reasonable men adapt themselves to the world.
> Unreasonable men adapt the world to themselves.
> That's why all progress depends on unreasonable men."
>
--
Have a nice day,
Timofey.
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