Re: reading an empty directory after reboot is very slow
Hi.
On Tue, Apr 14, 2015 at 08:58:20AM +0200, Petter Adsen wrote:
> On Mon, 13 Apr 2015 15:41:03 +0200
> Vincent Lefevre <vincent@vinc17.net> wrote:
>
> > On 2015-04-13 14:45:25 +0200, Loïc Grenié wrote:
> > > 2015-04-13 14:39 GMT+02:00 Vincent Lefevre <vincent@vinc17.net>:
> > > > The problem is that this operation is (always?) very slow:
> > > > something like 100 seconds (1 minute and 40 seconds). It has been
> > > > reproducible for several months. The logs show nothing during
> > > > this operation.
> > > >
> > > > Any idea?
> > >
> > > Maybe the directory is very large (even though its empty). Try
> > >
> > > ls -ld tmp.
> > >
> > > and see if the file "tmp" is large.
> >
> > Thanks! I didn't know that (I thought that the file system would
> > automatically "optimize" directories when files are removed, so
> > I've never looked closely at their size). Indeed:
> >
> > ypig:~/eftests> ls -ld tmp
> > drwxr-xr-x 2 vlefevre vlefevre 29655040 2015-04-13 15:25:55 tmp/
>
> Can someone please enlighten me as to why the entry for this directory
> is so large, even though it is empty? Since it's apparently obvious to
> everyone else, I would very much like to know :)
A case study:
$ mkdir tmp
$ du -sxh tmp
4.0K tmp
$ for x in {1..100000}; do touch tmp/$x; done
$ du -sxh tmp
2.1M tmp
$ find tmp -type f | xargs rm
$ du -sxh tmp
2.1M tmp
$ ls tmp | wc -l
0
Removing files from the directory does not change directory's inode
size. If using ext4, at least.
Reco
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