From: Nicholas Piggin <npiggin@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Johannes Weiner <hannes@cmpxchg.org>, Jan Kara <jack@suse.cz>,
Rik van Riel <riel@redhat.com>, linux-mm <linux-mm@kvack.org>
Subject: Re: page_waitqueue() considered harmful
Date: Thu, 29 Sep 2016 23:54:48 +1000 [thread overview]
Message-ID: <20160929235448.62197e3e@roar.ozlabs.ibm.com> (raw)
In-Reply-To: <20160929131635.GY5016@twins.programming.kicks-ass.net>
On Thu, 29 Sep 2016 15:16:35 +0200
Peter Zijlstra <peterz@infradead.org> wrote:
> On Thu, Sep 29, 2016 at 10:55:44PM +1000, Nicholas Piggin wrote:
> > On Thu, 29 Sep 2016 10:01:30 +0200
> > Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > > On Tue, Sep 27, 2016 at 09:54:12AM +0100, Mel Gorman wrote:
> > > > On Tue, Sep 27, 2016 at 09:30:55AM +0200, Peter Zijlstra wrote:
> > > > Simple is relative unless I drastically overcomplicated things and it
> > > > wouldn't be the first time. 64-bit only side-steps the page flag issue
> > > > as long as we can live with that.
> > >
> > > So one problem with the 64bit only pageflags is that they do eat space
> > > from page-flags-layout, we do try and fit a bunch of other crap in
> > > there, and at some point that all will not fit anymore and we'll revert
> > > to worse.
> > >
> > > I've no idea how far away from that we are for distro kernels. I suppose
> > > they have fairly large NR_NODES and NR_CPUS.
> >
> > I know it's not fashionable to care about them anymore, but it's sad if
> > 32-bit architectures miss out fundamental optimisations like this because
> > we're out of page flags. It would also be sad to increase the size of
> > struct page because we're too lazy to reduce flags. There's some that
> > might be able to be removed.
>
> I'm all for cleaning some of that up, but its been a long while since I
> poked in that general area.
Forgive my rant! Cleaning page flags is a topic of its own...
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next prev parent reply other threads:[~2016-09-29 13:55 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-26 20:58 page_waitqueue() considered harmful Linus Torvalds
2016-09-26 21:23 ` Rik van Riel
2016-09-26 21:30 ` Linus Torvalds
2016-09-26 23:11 ` Kirill A. Shutemov
2016-09-27 1:01 ` Rik van Riel
2016-09-27 7:30 ` Peter Zijlstra
2016-09-27 8:54 ` Mel Gorman
2016-09-27 9:11 ` Kirill A. Shutemov
2016-09-27 9:42 ` Mel Gorman
2016-09-27 9:52 ` Minchan Kim
2016-09-27 12:11 ` Kirill A. Shutemov
2016-09-29 8:01 ` Peter Zijlstra
2016-09-29 12:55 ` Nicholas Piggin
2016-09-29 13:16 ` Peter Zijlstra
2016-09-29 13:54 ` Nicholas Piggin [this message]
2016-09-29 15:05 ` Rik van Riel
2016-09-27 8:03 ` Jan Kara
2016-09-27 8:31 ` Mel Gorman
2016-09-27 14:34 ` Peter Zijlstra
2016-09-27 15:08 ` Nicholas Piggin
2016-09-27 16:31 ` Linus Torvalds
2016-09-27 16:49 ` Peter Zijlstra
2016-09-28 10:45 ` Mel Gorman
2016-09-28 11:11 ` Peter Zijlstra
2016-09-28 16:10 ` Linus Torvalds
2016-09-29 13:08 ` Peter Zijlstra
2016-10-03 10:47 ` Mel Gorman
2016-09-27 14:53 ` Nicholas Piggin
2016-09-27 15:17 ` Nicholas Piggin
2016-09-27 16:52 ` Peter Zijlstra
2016-09-27 17:06 ` Nicholas Piggin
2016-09-28 7:05 ` Peter Zijlstra
2016-09-28 11:05 ` Paul E. McKenney
2016-09-28 11:16 ` Peter Zijlstra
2016-09-28 12:58 ` Paul E. McKenney
2016-09-29 1:31 ` Nicholas Piggin
2016-09-29 2:12 ` Paul E. McKenney
2016-09-29 6:21 ` Peter Zijlstra
2016-09-29 6:42 ` Nicholas Piggin
2016-09-29 7:14 ` Peter Zijlstra
2016-09-29 7:43 ` Peter Zijlstra
2016-09-28 7:40 ` Mel Gorman
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