Re: large file IO starving ls -l

Roland Kuhn (rkuhn@e18.physik.tu-muenchen.de)
Sun, 4 Aug 2002 08:14:55 +0200 (CEST)


On Sat, 3 Aug 2002, Linus Torvalds wrote:

> In article <Pine.LNX.4.44.0208032253260.23040-100000@pc40.e18.physik.tu-muenchen.de>,
> Roland Kuhn <rkuhn@e18.physik.tu-muenchen.de> wrote:
> >
> >Now the question is: who keeps ls from returning? The command never hits
> >the disk (reads in above histogram do not increase), but stays for many
> >seconds (up to one minute) in state D.
>
> ext2 used to have similar issues with the superblock lock - where things
> like block allocation (very much in the write path) would grab the
> superblock lock, and completely destroy interactive feel even for
> processes that didn't need to do IO, because the superblock lock was
> often grabbed even if the data was actually cached (sb locking needed
> just to _look_up_ the physical block so that you could look up the
> cached data in the buffer cache).
>
> Al Viro largely fixed in for ext2, which now uses lock_super() a lot
> less. But a lot of filesystems are based on the old ext2 locking, and
> may have inherited some of the worst parts..
>
Thanks for the hint, I will try to have a look at the reiserfs code. Could
you give me a hint where this lock usually is taken?

Ciao,
Roland

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