Re: [PATCH 10/10] mm: per device dirty threshold

From: Andrew Morton
Date: Tue Apr 24 2007 - 06:02:27 EST

On Tue, 24 Apr 2007 11:47:20 +0200 Miklos Szeredi <miklos@xxxxxxxxxx> wrote:

> > Ahh, now I see; I had totally blocked out these few lines:
> >
> > pages_written += write_chunk - wbc.nr_to_write;
> > if (pages_written >= write_chunk)
> > break; /* We've done our duty */
> >
> > yeah, those look dubious indeed... And reading back Neil's comments, I
> > think he agrees.
> >
> > Shall we just kill those?
> I think we should.
> Athough I'm a little afraid, that Akpm will tell me again, that I'm a
> stupid git, and that those lines are in fact vitally important ;)

It depends what they're replaced with.

That code is there, iirc, to prevent a process from getting stuck in
balance_dirty_pages() forever due to the dirtying activity of other

hm, we ask the process to write write_chunk pages each go around the loop.
So if it wrote write-chunk/2 pages on the first pass it might end up writing
write_chunk*1.5 pages total. I guess that's rare and doesn't matter much
if it does happen - the upper bound is write_chunk*2-1, I think.
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