linux-kernel - Re: 回复: [PATCH] mm:vmscan: fix extra adjustment for lruvec's nonresident

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Date:   Fri, 1 Oct 2021 12:43:56 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     解 咏梅 <yongmeixie@...mail.com>
Cc:     "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 回复: [PATCH] mm:vmscan: fix extra adjustment for lruvec's
 nonresident_age in case of reactivation

On Wed, Sep 22, 2021 at 02:27:24PM +0000, 解 咏梅 wrote:
> But now, move_pages_to_lru didn't increase nonresident age for active rotation.
> Back toinactive age, VM ONLY care about the pages left inactive lru, AKA activation and reclaiming.
> Anyway reactivation is rare case, so whatever it contributes to nonresident age or not is ok to me.
> 
> But I am interested the logic how to guess the pages will be referenced again in the future.
> If active reactivation does matter to nonresident age. why not active rotation? But, currently it doesn't.

Can you point me to the code you're referring to? Looking at
move_pages_to_lru(), any pages with PageActive() set count toward the
non-resident age. That means activations from the inactive list, as
well as rotations on the active list, increase the nonresident age.

As to your question which one is right: the original workingset patch
was wrong not to count activations and reactivations. If we see a page
referenced in memory, it means it's hotter than the page that's not
refaulting -> nonresident age increses.

So the code as it is now looks correct to me.

Thanks