Re: [PATCH 6/7] writeback: separate starting of sync vs opportunistic writeback

Jens Axboe
2009-09-15T13:17:11Z

On Tue, Sep 15 2009, Christoph Hellwig wrote:
> On Tue, Sep 15, 2009 at 03:04:19PM +0200, Jens Axboe wrote:
> >
> > > Let's have a look at the flags in wbc:
> > > nonblocking - Currently only set by direct callers of ->writepage() BUT
> > > originally wb_kupdate() and background_writeout() also
> > > set this flag. Since filesystems and write_cache_pages()
> > > use the flag we should set it for equivalent writeouts as
> > > well. This should be fixed...
> >
> > Since this is all handled by the dedicated thread now, dropping the
> > nonblocking bit was on purpose. What would the point be, except for
> > stopping pdflush being blocked on request allocation?
>
> Note that this flag just caused utter mess traditionally. btrfs decided
> to ignore it completely and ext4 partially. Removing this check in
> XFS increases large bufferd write loads massively.
>
> Just half-removing it is a bad idea, though - if you don't set it
> anymore please kill it entirely.

I haven't touched it, except removing it from the caller where it
doesn't make sense anymore. If you think we should kill it completely,
then lets look at that in a few days. I've got more than enough stuff
queued up for inclusion now that I need to test and verify before doing
even more cleanups/changes :-)

--
Jens Axboe