linux-kernel - Re: [RFC v1] mm: add page preemption

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Message-ID: <20191020152400.GA9214@bombadil.infradead.org>
Date:   Sun, 20 Oct 2019 08:24:00 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     linux-mm <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Jan Kara <jack@...e.cz>
Subject: Re: [RFC v1] mm: add page preemption

On Sun, Oct 20, 2019 at 09:43:04PM +0800, Hillf Danton wrote:
> First on the page side, page->prio that is used to mirror the prio
> of page owner tasks is added, and a couple of helpers for setting,
> copying and comparing page->prio to help to add pages to lru.

Um, no.  struct page is 64 bytes and shall remain so without a very very
good reason.

> @@ -197,6 +198,10 @@ struct page {
>  	/* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */
>  	atomic_t _refcount;
>  
> +#ifdef CONFIG_PAGE_PREEMPTION
> +	int prio; /* mirror page owner task->prio */
> +#endif
> +
>  #ifdef CONFIG_MEMCG
>  	struct mem_cgroup *mem_cgroup;
>  #endif