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SubjectRe: [RFC] Heads up on sys_fallocate()
On Tue 06-03-07 06:36:09, Ulrich Drepper wrote:
> Christoph Hellwig wrote:
> > fallocate with the whence argument and flags is already quite complicated,
> > I'd rather have another call for placement decisions, that would
> > be called on an fd to do placement decissions for any further allocations
> > (prealloc, write, etc)
> Yes, posix_fallocate shouldn't be made more complicated. But I don't
> understand why requesting linear layout of the blocks should be an
> option. It's always an advantage if the blocks requested this way are
> linear on disk. So, the kernel should always do its best to make this
> happen, without needing an additional option.
Actually, it's not that simple. You want linear layout of blocks you are
going to read. That is not necessary a linear layout of blocks in a single
file - trace sometime a start of some complicated app like KDE. You find
it's seeking like a hell because it needs a few blocks from a ton of
distinct files (shared libs, config files, etc). As these files are mostly
read only, it's advantageous to interleave them on disk or at least keep
them close.

Jan Kara <>
SuSE CR Labs
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