linux-kernel - Re: [PATCH][RFC] PM / Hibernate: Feed NMI wathdog when creating snapshot

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Date:   Tue, 15 Aug 2017 14:41:19 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-mm@...ck.org, linux-pm@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH][RFC] PM / Hibernate: Feed NMI wathdog when creating
 snapshot

On Tue 15-08-17 01:19:16, Chen Yu wrote:
[...]
> @@ -2561,8 +2562,10 @@ void mark_free_pages(struct zone *zone)
>  			unsigned long i;
>  
>  			pfn = page_to_pfn(page);
> -			for (i = 0; i < (1UL << order); i++)
> +			for (i = 0; i < (1UL << order); i++) {
>  				swsusp_set_page_free(pfn_to_page(pfn + i));
> +				touch_nmi_watchdog();
> +			}

this is rather excessive. Why don't you simply call touch_nmi_watchdog
once per every 1000 pages? Or once per free_list entry?

Moreover why don't you need to touch_nmi_watchdog in the loop over all
pfns in the zone (right above this loop)?
-- 
Michal Hocko
SUSE Labs