linux-kernel - Re: [PATCH 0/5] mm: workingset: radix tree subtleties & single-page file refaults

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Message-ID: <20161026182942.GA18258@cmpxchg.org>
Date:   Wed, 26 Oct 2016 14:29:42 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.cz>,
        Dave Jones <davej@...emonkey.org.uk>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...com>
Subject: Re: [PATCH 0/5] mm: workingset: radix tree subtleties & single-page
 file refaults

On Wed, Oct 26, 2016 at 11:18:52AM -0700, Linus Torvalds wrote:
> On Mon, Oct 24, 2016 at 11:47 AM, Johannes Weiner <hannes@...xchg.org> wrote:
> >
> > How about this instead: given that we already mark the shadow entries
> > exceptional, and the exceptional bit is part of the radix tree API,
> > can we just introduce a node->exceptional counter for those entries
> > and have the radix tree code assist us with that instead? It adds the
> > counting for non-shadow exceptional entries as well (shmem swap slots,
> > and DAX non-page entries), unfortunately, but this is way cleaner. It
> > also makes mapping->nrexceptional and node->exceptional consistent in
> > DAX (Jan, could you please double check the accounting there?)
> >
> > What do you think? Lightly tested patch below.
> 
> This certainly looks way better to me. I didn't *test* it, but it
> doesn't make me scratch my head the way your previous patch did.

Awesome, thanks. I'll continue to beat on this for a while and then
send it on to Andrew.