Messages in this thread | | | From | Rob Landley <> | Subject | Re: Is there a "make hole" (truncate in middle) syscall? | Date | Thu, 11 Dec 2003 14:32:12 -0600 |
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On Thursday 11 December 2003 13:48, Jörn Engel wrote: > On Thu, 11 December 2003 11:15:28 -0800, Hua Zhong wrote: > > > The abstract interface for make_hole() is simple, but it turns into a > > > pretty expensive filesystem operation, I think. After many cycles of > > > free/allocate, your file would be badly fragmented across the > > > filesystem. > > > > Understood. Two filesystems we are using: tmpfs and ext3. For the > > former, fragmentation doesn't matter. > > > > Hey, I think when I get some cycles I can try to implement this for > > tmpfs (since it's simpler) myself, and post a patch. :-) But before > > that, I want to make sure it's doable. > > If you really do it, please don't add a syscall for it. Simply check > each written page if it is completely filled with zero. (This will be > a very quick check for most pages, as they will contain something > nonzero in the first couple of words)
Cache poisoning, streaming writes to large RAID arrays... There are about 8 zllion reasons not to do this. Really. (It defeats the whole purpose of DMA, doesn't it?)
> Jörn
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