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bug#25930: optimize mv for multiple bind mounts
From: |
Ruediger Meier |
Subject: |
bug#25930: optimize mv for multiple bind mounts |
Date: |
Thu, 2 Mar 2017 10:51:40 +0100 |
User-agent: |
KMail/1.9.10 |
Hi,
I have two bind mounts of the same filesystem
$ grep "/tmp" /etc/fstab
/dev/vg0/tmpdirs /mnt/tmpdirs ext4
acl,user_xattr,usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0 1 2
/mnt/tmpdirs/tmp /tmp none bind 0 0
/mnt/tmpdirs/var/tmp /var/tmp none bind 0 0
Using mv to move files between the bind mounts makes a slow copy:
$ time mv /var/tmp/BIGFILE /tmp/
real 0m0.622s
user 0m0.001s
sys 0m0.621s
In theory mv could know somehow that's the same filesystem
and do it like this:
$ time mv /mnt/tmpdirs/tmp/BIGFILE /mnt/tmpdirs/var/tmp/
real 0m0.004s
user 0m0.001s
sys 0m0.003s
Would it be possible to optimize mv regarding bind mounts? Or perhaps
are there other filesystems which do this better than ext4? Specially
the case that the original whole filesystem (/mnt/tmpdirs) is umounted
should work too somewhow.
cu,
Rudi
- bug#25930: optimize mv for multiple bind mounts,
Ruediger Meier <=