linux-kernel - Re: splice: move balance_dirty_pages_ratelimited() outside of splice actor

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Message-ID: <20070612124449.GD18832@kernel.dk>
Date:	Tue, 12 Jun 2007 14:44:50 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: splice: move balance_dirty_pages_ratelimited() outside of    splice actor

On Tue, Jun 12 2007, Peter Zijlstra wrote:
> On Tue, 2007-06-12 at 14:10 +0200, Jens Axboe wrote:
> > On Tue, Jun 12 2007, Peter Zijlstra wrote:
> > > On Tue, 2007-06-12 at 13:31 +0200, Jens Axboe wrote:
> > > 
> > > > Would you prefer this change, then? I'd prefer keeping the current code,
> > > > unless it's absolutely critical that we call
> > > > balance_dirty_pages_ratelimited() for each and every page instead of eg
> > > > every 16 pages here.
> > > 
> > > For that we should call:
> > >   balance_dirty_pages_ratelimited_nr(mapping, nr);
> > > 
> > > Which is ok, for small nr.
> > 
> > OK, then this should be better:
> > 
> > diff --git a/fs/splice.c b/fs/splice.c
> > index 25ec9c8..ed40967 100644
> > --- a/fs/splice.c
> > +++ b/fs/splice.c
> > @@ -844,6 +883,9 @@ generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
> >  	sd.file = out;
> >  	ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
> >  	if (ret > 0) {
> > +		unsigned long nr_pages;
> > +
> > +		nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
> 
> perhaps?
> 	nr_pages = DIV_ROUND_UP(ret, PAGE_CACHE_SIZE); 
> 
> not sure how horrid that turns out to be; you never know with gcc.

Well, I think such macros are horribly ugly and that the original code
is MUCH easier to read.

-- 
Jens Axboe

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