On 01/31/2013 06:43 AM, Thomas Habets wrote: > Hi. > > I've had some files on an XFS filesystem that use way > more blocks than they need. > > That is, st_size=50MB and st_blocks*512= about 68MB. > > The files were downloaded with wget on a somewhat unreliable 3G > connection (50-500kBps) and sometimes defragging (xfs_fsr) fixes it, > but > sometimes not. > > If st_blocks*512<st_size then it could be sparse files, but this is > the opposite. So... preallocation? > Yes, here's a thread (one of probably several examples) that discusses the behavior and how the extra space is not permanent, but can hang around for a bit: http://oss.sgi.com/archives/xfs/2012-03/msg00145.html > "df" before and after deleting a bunch of these files shows that the > st_blocks is what it cares about. Would the preallocation (if that's > what it is) be reclaimed if the fs started to run out of space? > I don't think so at the moment, but preallocation is throttled as the filesystem free space becomes more limited. We've recently added speculative prealloc tracking that performs background trimming on a timer controlled via: /proc/sys/fs/xfs/speculative_prealloc_lifetime ... and can be used in the future to explicitly reclaim extra space lying around when the filesystem is full. Brian > If not preallocation, then what? > > Note st_blocks is 134656 and xfs_bmap shows 97663 blocks. > > $ ls -l foo > -rw-r--r-- 1 root root 50000000 Jan 29 01:32 foo > $ du -h foo > 66M foo > $ stat foo > File: `foo' > Size: 50000000 Blocks: 134656 IO Block: 4096 regular file > Device: fe04h/65028d Inode: 68688483 Links: 1 > Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) > Access: 2013-01-30 18:56:18.603278346 +0000 > Modify: 2013-01-29 01:32:51.000000000 +0000 > Change: 2013-01-31 11:38:10.892330145 +0000 > Birth: - > $ xfs_bmap foo > foo: > 0: [0..97663]: 44665840..44763503 > > -- > typedef struct me_s { > char name[] = { "Thomas Habets" }; > char email[] = { "thomas@xxxxxxxxxxxx" }; > char kernel[] = { "Linux" }; > char *pgpKey[] = { "http://www.habets.pp.se/pubkey.txt"; }; > char pgp[] = { "A8A3 D1DD 4AE0 8467 7FDE 0945 286A E90A AD48 E854" }; > char coolcmd[] = { "echo '. ./_&. ./_'>_;. ./_" }; > } me_t; > > _______________________________________________ > xfs mailing list > xfs@xxxxxxxxxxx > http://oss.sgi.com/mailman/listinfo/xfs > _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
