Re: [RFC] Heads up on sys_fallocate()

From: Christoph Hellwig
Date: Tue Mar 06 2007 - 09:48:36 EST


On Tue, Mar 06, 2007 at 06:36:09AM -0800, 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.

There are HPC workloads where you have multi writers on multiple machines
that write to different parts of a file. You preferably want each
of those regions in separate allocation groups. (Or tell the customers
to use separate files for the regions..)
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