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

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Date:   Wed, 26 Oct 2016 11:18:52 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Johannes Weiner <hannes@...xchg.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 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.

               Linus