linux-kernel - Re: [PATCH] mm,page_alloc,cma: conditionally prefer cma pageblocks for movable allocations

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Message-ID: <20200311232141.GA181064@carbon.DHCP.thefacebook.com>
Date:   Wed, 11 Mar 2020 16:21:41 -0700
From:   Roman Gushchin <guro@...com>
To:     Vlastimil Babka <vbabka@...e.cz>
CC:     Rik van Riel <riel@...riel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <kernel-team@...com>, Qian Cai <cai@....pw>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH] mm,page_alloc,cma: conditionally prefer cma pageblocks
 for movable allocations

On Thu, Mar 12, 2020 at 12:03:58AM +0100, Vlastimil Babka wrote:
> On 3/11/20 11:58 PM, Roman Gushchin wrote:
> >> 
> >> I agree it should be in the noise. But please do put it behind CONFIG_CMA
> >> #ifdef. My x86_64 desktop distro kernel doesn't have CONFIG_CMA. Even if this is
> >> effectively no-op with __rmqueue_cma_fallback() returning NULL immediately, I
> >> think the compiler cannot eliminate the two zone_page_state()'s which are
> >> atomic_long_read(), even if it's just ultimately READ_ONCE() here, that's a
> >> volatile cast which means elimination not possible AFAIK? Other architectures
> >> might be even more involved.
> > 
> > I agree.
> > 
> > Andrew,
> > can you, please, squash the following diff into the patch?
> 
> Thanks,
> 
> then please add to the result
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thank you!