linux-kernel - Re: [PATCH v5 0/6] Introduce ZONE

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Message-ID: <20160831080300.GB22757@js1304-P5Q-DELUXE>
Date:   Wed, 31 Aug 2016 17:03:00 +0900
From:   Joonsoo Kim <iamjoonsoo.kim@....com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Laura Abbott <lauraa@...eaurora.org>,
        Minchan Kim <minchan@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Nazarewicz <mina86@...a86.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 0/6] Introduce ZONE_CMA

On Tue, Aug 30, 2016 at 04:09:37PM +0530, Aneesh Kumar K.V wrote:
> Joonsoo Kim <js1304@...il.com> writes:
> 
> > 2016-08-29 18:27 GMT+09:00 Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>:
> >> js1304@...il.com writes:
> >>
> >>> From: Joonsoo Kim <iamjoonsoo.kim@....com>
> >>>
> >>> Hello,
> >>>
> >>> Changes from v4
> >>> o Rebase on next-20160825
> >>> o Add general fix patch for lowmem reserve
> >>> o Fix lowmem reserve ratio
> >>> o Fix zone span optimizaion per Vlastimil
> >>> o Fix pageset initialization
> >>> o Change invocation timing on cma_init_reserved_areas()
> >>
> >> I don't see much information regarding how we interleave between
> >> ZONE_CMA and other zones for movable allocation. Is that explained in
> >> any of the patch ? The fair zone allocator got removed by
> >> e6cbd7f2efb433d717af72aa8510a9db6f7a7e05
> >
> > Interleaving would not work since the fair zone allocator policy is removed.
> > I don't think that it's a big problem because it is just matter of
> > timing to fill
> > up the memory. Eventually, memory on ZONE_CMA will be fully used in
> > any case.
> 
> Does that mean a CMA allocation will now be slower because in most case we
> will need to reclaim ? The zone list will now have ZONE_CMA in the
> beginning right ?

ZONE_CMA will be used first but I don't think that CMA allocation will
be slower. In most case, memory would be fully used (usually
by page cache). So, we need reclaim or migration in any case.

Thanks.