linux-kernel - Re: [RFC 3/7] mm: introduce MADV

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Date:   Thu, 30 May 2019 09:45:07 +0900
From:   Minchan Kim <minchan@...nel.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tim Murray <timmurray@...gle.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Daniel Colascione <dancol@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Sonny Rao <sonnyrao@...gle.com>,
        Brian Geffon <bgeffon@...gle.com>
Subject: Re: [RFC 3/7] mm: introduce MADV_COLD

On Tue, May 28, 2019 at 10:54:32PM +0800, Hillf Danton wrote:
> 
> On Mon, 20 May 2019 12:52:50 +0900 Minchan Kim wrote:
> > +unsigned long reclaim_pages(struct list_head *page_list)
> > +{
> > +	int nid = -1;
> > +	unsigned long nr_isolated[2] = {0, };
> > +	unsigned long nr_reclaimed = 0;
> > +	LIST_HEAD(node_page_list);
> > +	struct reclaim_stat dummy_stat;
> > +	struct scan_control sc = {
> > +		.gfp_mask = GFP_KERNEL,
> > +		.priority = DEF_PRIORITY,
> > +		.may_writepage = 1,
> > +		.may_unmap = 1,
> > +		.may_swap = 1,
> > +	};
> > +
> > +	while (!list_empty(page_list)) {
> > +		struct page *page;
> > +
> > +		page = lru_to_page(page_list);
> > +		list_del(&page->lru);
> > +
> > +		if (nid == -1) {
> > +			nid = page_to_nid(page);
> > +			INIT_LIST_HEAD(&node_page_list);
> > +			nr_isolated[0] = nr_isolated[1] = 0;
> > +		}
> > +
> > +		if (nid == page_to_nid(page)) {
> > +			list_add(&page->lru, &node_page_list);
> > +			nr_isolated[!!page_is_file_cache(page)] +=
> > +						hpage_nr_pages(page);
> > +			continue;
> > +		}
> > +
> Now, page's node != nid and any page on the node_page_list has
> node == nid. 
> > +		nid = page_to_nid(page);
> 
> After updating nid, we get the node id of the isolated pages lost.
> 
> > +
> > +		mod_node_page_state(NODE_DATA(nid), NR_ISOLATED_ANON,
> > +					nr_isolated[0]);
> > +		mod_node_page_state(NODE_DATA(nid), NR_ISOLATED_FILE,
> > +					nr_isolated[1]);
> > +		nr_reclaimed += shrink_page_list(&node_page_list,
> > +				NODE_DATA(nid), &sc, TTU_IGNORE_ACCESS,
> 
> And nid no longer matches the node of the pages to be shrunk.
> 
> > +				&dummy_stat, true);
> > +		while (!list_empty(&node_page_list)) {
> > +			struct page *page = lru_to_page(page_list);
> 
> Non-empty node_page_list will never become empty if pages are deleted
> only from the page_list.

Sure.
They were last minute change. I will fix it.

Thanks for the review!