Re: journaling & VM (was: Re: reiserfs being part of the kernel: it's not just the code)

Stephen C. Tweedie
2000-06-07T10:10:33Z

Hi,

On Tue, Jun 06, 2000 at 08:06:38PM -0300, Rik van Riel wrote:
>
> > journaling itself, but the transactional requirements which are
> > the problem --- basically the VM cannot do _anything_ about
> > individual pages which are pinned by a transaction, but rather
> > we need a way to trigger a filesystem flush, AND to prevent more
> > dirtying of pages by the filesystem (these are two distinct
> > problems), or we just lock up under load on lower memory boxes.
>
> This is especially tricky in the case of a large mmap()ed
> file. We'll have to restrict the maximum number of read-write
> mapped pages from such a file in order to keep the system
> stable...

We need to restrict *all* pinned pages. That includes writable
pages on a transactional filesystem, but also includes metadata
being used as part of an existing transaction, as well as any
potential metadata which *might* be used in the future by that
transaction.

> Indeed we need this. Since I seem to be coordinating the VM
> changes at the moment anyway, I'd love to work together with
> the journaling folks on solving this problem...

OK, I'll look up the old writeups I did with Chris about this.

Cheers,
Stephen