[Tux3] Deferred Namespace Operations
zenczykowski at gmail.com
Mon Nov 10 23:50:55 PST 2008
I understood that one of the benefits of deferred creation, was that a
later deletion could possibly end up with no disk i/o. I was just
pointing out, that this is still not quite the case, since we need to
have enough data to later release the files data blocks... although I
guess a deleted files data-blocks could be allocated while only
marking their 'use' in in-memory-state (never writing it to disk).
However, this seems highly error-prone and not worth it. As such the
above optimization can only really be done if we're deleting a file to
which there are no more open references...
On Mon, Nov 10, 2008 at 23:15, Daniel Phillips <phillips at phunq.net> wrote:
> On Monday 10 November 2008 13:56, Maciej Żenczykowski wrote:
>> > two. A file that is created and deleted before a delta transition
>> > takes place will not only never appear on disk, it will not even appear
>> > in a cached disk block.
>> I'd like to point out, that if you create a file, open it, then delete
>> it, you can then still use it to store temporary data - this is indeed
>> a common use case. However the amount of data storage may very well
>> exceed what you would be willing to store in ram, and thus you would
>> want to be able to write this data out to disk, even though the file
>> itself doesn't exist any more... Some sort of swap-like behaviour???
> You mean an orphan temporary file? I think we just need to make sure
> that works as it is supposed to. It is reasonable for file data of
> such a file to be transferred to disk just like any other file, even
> though the file is unlinked. We just need to be sure that it will get
> cleaned up like any other orphan.
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