On 2/2/16 4:32 PM, Dilip Simha wrote: > Hi, > > I have a question regarding speculated preallocation in XFS, w.r.t > kernel version: 3.16.0-46-generic. I am using Swift version: 1.0 and > mkfs.xfs version 3.2.1 > > When I write a 256KiB file to Swift, I see that the underlying XFS > uses 3x the amount of space/blocks to write that data. Upon > performing detailed experiments, I see that when Swift uses fallocate > (default approach), XFS doesn't reclaim the preallocated blocks that > XFS allocated. Swift fallocate doesn't exceed the body size(256 > KiB). > > Interestingly, when either allocsize=4k or when swift doesn't use > fallocate, XFS doesn't consume additional space. > > Can you please let me know if this is a known bug and if its fixed in > the later versions? Can you clarify the exact sequence of events? i.e. - xfs_io -f -c "fallocate 0 256k" -c "pwrite 0 256k" somefile leads to unreaclaimed preallocation, while xfs_io -f -c "pwrite 0 256k" somefile does not? Or is it some other sequence? I don't have a 3.16 handy to test, but if you can describe it in more detail that'd help. Some of this is influenced by fs geometry, too so xfs_info output would be good, along with any mount options you might be using. Are you preallocating with or without KEEP_SIZE? -Eric _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
