Re: Deletion of big files...

Pavel Machek (pavel@bug.ucw.cz)
Sat, 15 May 1999 21:38:23 +0200


Hi!

> I have noticed that when I delete a big file (say 800MB), with a rm
> command, for example, the rm command does not return until the file has
> been deleted (or so it seems). With small files, this is almost
> inmediate, but with files which are say 800 megs in size, this can
> easily be 10 seconds (_seconds_, it's right) till I get the prompt
> again, on a P2-333.
>
> In other Unices, like IRIX, the rm command returns _inmediately_, no
> matter the size of the file.
>
> Looks to me like the unlink syscall is somewhat synchronous, and it
> shouldn't, or does it? For this concrete issue, it could be easily
> solved by the unlink syscall starting a thread to unlink the big file,
> while the rest of the system keeps running normally. But I suppose it's
> not only an issue of the unlink syscall, but more...
>
> I'm probably saying nonsense WRT the solution, but the problem _is_
> there. Any answers/constructive-criticisms?

Well, if you went for completely async unlink...

rm bigfile
<use of lots of disk space>

could fail due to "out of disk space", where sync remove does not have
this problem.

So it is not as easy as it seems.

Pavel
PS: I could imagine Irix being faster not because asynchrony, but
because their fs is more effective for this concrete issue.

-- 
I'm really pavel@ucw.cz. Look at http://195.113.31.123/~pavel.          Pavel
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