Re: [PATCH] Invalidate_inodes can be very slow

[Kirill Korotaev <kk@sw.ru>]

> At some point in the past, I wrote:
> >> Sorry if I was unclear, I had in mind SMP performance testing of mount
> >> and unmount -heavy workloads, like uni setups with many automounted
> >> fs's, not stability testing per se.
>
> On Mon, Oct 13, 2003 at 04:02:20PM +0400, Kirill Korotaev wrote:
> > Oh, sorry for misunderstanding.
> > In our internal testcase on 8-CPU 8Gb RAM machine with 4gb split kernel
> > w/o this patch mount/umount test longs in many-many (>10) times longer.
> > Moreover, during the test machine is very slow (due to lock_kernel)
> > and typing simple commands takes up to 30 seconds or so.
> > I think such a long hangs are due to number of umounts executed
> > subsequently. But ofcourse it's not numbers, just for you to know where
> > the patch comes from :)
>
> Is this testcase available and/or trivial? Actually, even if it's trivial
> it might just save us the pain of writing the scripts ourselves.
no, testcase is not available :( And it uses functionality
not available in mainstream kernel. But the problem can be hit with
very simple script instead:

1. mount N filesystems.
2. work on them, so that inode cache grows to its maximum
possible size (it was 1,000,000 of inodes in our case).
3. umount these filesystems.

During operation #3 node is very slow and it is quite noticable
on ssh console when typing commands.

Kirill