Hello,
I am trying to write sequences of contiguous files in XFS to minimize
the drive head seeks that must occur during file reads. Using the
XFS_RESVSP64 ioctl to reserve the set of files ahead of time, I am able to
get individual files allocated with contiguous extents. However, the
allocation of one file versus another (reserved immediately after each
other) seems to be somewhat erratic. Is there a way to guarantee or further
lock the allocation of one file with respect to another in a contiguous
manner? Looking at xfs_vnodeops.c and xfs_bmap.c could this be possibly be
achieved by initializing the firstfsb structure in xfs_alloc_file_space()
only in the first reserve call for a group allocation? The value of this
structure could be maintained for consecutive calls to allow the contiguous
allocation of a group of files based on the preceeding reserve ioctl. This
behavior could be added as an additional ioctl call (RESVSP64CONTIG?) to
maintain the current working code.
I am going to experiment with this, but I would appreciate
suggestions/comments. Thanks.
Rick Smith
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