Posted Nov 30, 2011 21:16 UTC (Wed) by walex
In reply to: bigalloc
Parent article: Improving ext4: bigalloc, inline data, and metadata checksums
Note that 'ext4' supports extents, so files can get allocated with very large contiguous extents already, for example for a 70MB file:
# du -sm /usr/share/icons/oxygen/icon-theme.cache
# filefrag /usr/share/icons/oxygen/icon-theme.cache
/usr/share/icons/oxygen/icon-theme.cache: 1 extent found
# df -T /usr/share/icons/oxygen/icon-theme.cache
Filesystem Type 1M-blocks Used Available Use% Mounted on
/dev/sda3 ext4 25383 12558 11545 53% /
But so far the free space has been tracked in block-sized units,
and the new thing seems to change the amount of free space accounted
for by each bit in the free space bitmap.
Which means that as surmised the granularity of allocation has changed
(for example minimum extent size).
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