linux-kernel - Re: [PATCH v5 3/6] mm/cma: populate ZONE

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Message-ID: <20160928053408.GD22706@js1304-P5Q-DELUXE>
Date:   Wed, 28 Sep 2016 14:34:08 +0900
From:   Joonsoo Kim <iamjoonsoo.kim@....com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        mgorman@...hsingularity.net, Laura Abbott <lauraa@...eaurora.org>,
        Minchan Kim <minchan@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Nazarewicz <mina86@...a86.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/6] mm/cma: populate ZONE_CMA

On Thu, Sep 22, 2016 at 05:59:46PM +0200, Vlastimil Babka wrote:
> On 09/22/2016 08:50 AM, Joonsoo Kim wrote:
> >On Thu, Sep 22, 2016 at 02:45:46PM +0900, Joonsoo Kim wrote:
> >>>
> >>> > /* Free whole pageblock and set its migration type to MIGRATE_CMA. */
> >>> > void __init init_cma_reserved_pageblock(struct page *page)
> >>> > {
> >>> > 	unsigned i = pageblock_nr_pages;
> >>> >+	unsigned long pfn = page_to_pfn(page);
> >>> > 	struct page *p = page;
> >>> >+	int nid = page_to_nid(page);
> >>> >+
> >>> >+	/*
> >>> >+	 * ZONE_CMA will steal present pages from other zones by changing
> >>> >+	 * page links so page_zone() is changed. Before that,
> >>> >+	 * we need to adjust previous zone's page count first.
> >>> >+	 */
> >>> >+	adjust_present_page_count(page, -pageblock_nr_pages);
> >>> >
> >>> > 	do {
> >>> > 		__ClearPageReserved(p);
> >>> > 		set_page_count(p, 0);
> >>> >-	} while (++p, --i);
> >>> >+
> >>> >+		/* Steal pages from other zones */
> >>> >+		set_page_links(p, ZONE_CMA, nid, pfn);
> >>> >+	} while (++p, ++pfn, --i);
> >>> >+
> >>> >+	adjust_present_page_count(page, pageblock_nr_pages);
> >>>
> >>> This seems to assign pages to ZONE_CMA on the proper node, which is
> >>> good. But then ZONE_CMA on multiple nodes will have unnecessary
> >>> holes in the spanned pages, as each will contain only a subset.
> >>
> >>True, I will fix it and respin the series.
> >
> >I now realize that it's too late to send full series for next
> >merge window. I will send full series after next merge window is closed.
> 
> I think there might still be rc8 thus another week.

Indeed. I will send full series, soon.

> 
> >Anyway, I'd like to confirm that following incremental patch will solve
> >your concern.
> 
> Yeah that should work, as long as single cma areas don't include multiple nodes?

Single cma areas cannot include multiple nodes at least until now.
There is a check that single cma area is on a single zone.

Thanks.

> 
> >Thanks.
> >
> >
> >------>8--------------
> > mm/cma.c | 25 ++++++++++++++++---------
> > 1 file changed, 16 insertions(+), 9 deletions(-)
> >
> >diff --git a/mm/cma.c b/mm/cma.c
> >index d69bdf7..8375554 100644
> >--- a/mm/cma.c
> >+++ b/mm/cma.c
> >@@ -146,22 +146,29 @@ static int __init cma_init_reserved_areas(void)
> > {
> >        int i;
> >        struct zone *zone;
> >-       unsigned long start_pfn = UINT_MAX, end_pfn = 0;
> >+       pg_data_t *pgdat;
> >
> >        if (!cma_area_count)
> >                return 0;
> >
> >-       for (i = 0; i < cma_area_count; i++) {
> >-               if (start_pfn > cma_areas[i].base_pfn)
> >-                       start_pfn = cma_areas[i].base_pfn;
> >-               if (end_pfn < cma_areas[i].base_pfn + cma_areas[i].count)
> >-                       end_pfn = cma_areas[i].base_pfn + cma_areas[i].count;
> >-       }
> >+       for_each_online_pgdat(pgdat) {
> >+               unsigned long start_pfn = UINT_MAX, end_pfn = 0;
> >
> >-       for_each_zone(zone) {
> >-               if (!is_zone_cma(zone))
> >+               for (i = 0; i < cma_area_count; i++) {
> >+                       if (page_to_nid(pfn_to_page(cma_areas[i].base_pfn)) !=
> 
> We have pfn_to_nid() (although the implementation is just like this).

Will fix.

Thanks.