linux-kernel - Re: [PATCH 1/1] mm: add swapiness= arg to memory.reclaim

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Message-ID: <dhhjw4h22q4ngwtxmhuyifv32zjd6z2relrcjgnxsw6zys3mod@o6dh5dy53ae3>
Date:   Thu, 7 Dec 2023 20:00:07 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     Dan Schatzberg <schatzberg.dan@...il.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Yosry Ahmed <yosryahmed@...gle.com>, Huan Yang <link@...o.com>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, Tejun Heo <tj@...nel.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Jonathan Corbet <corbet@....net>,
        Michal Hocko <mhocko@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        "Vishal Moola (Oracle)" <vishal.moola@...il.com>,
        Yue Zhao <findns94@...il.com>, Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 1/1] mm: add swapiness= arg to memory.reclaim

On Wed, Dec 06, 2023 at 08:28:56AM -0800, Dan Schatzberg <schatzberg.dan@...il.com> wrote:
> @@ -6902,12 +6913,33 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,
...
> +	int swappiness = -1;

Here you use a negative number...

> @@ -136,6 +136,9 @@ struct scan_control {
...
> +	/* Swappiness value for reclaim, if NULL use memcg/global value */
> +	int *swappiness;

... and here a NULL to denote the unset value.

I'd suggest unifying those. Perhaps the negative to avoid unnecessary dereferences.

Thanks,
Michal

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