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Date:   Thu, 25 Jul 2019 05:45:24 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        John Stultz <john.stultz@linaro.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Laura Abbott <labbott@redhat.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        Liam Mark <lmark@codeaurora.org>,
        Pratik Patel <pratikp@codeaurora.org>,
        Brian Starkey <Brian.Starkey@arm.com>,
        Vincent Donnefort <Vincent.Donnefort@arm.com>,
        Sudipto Paul <Sudipto.Paul@arm.com>,
        "Andrew F . Davis" <afd@ti.com>,
        Xu YiPing <xuyiping@hisilicon.com>,
        "Chenfeng (puck)" <puck.chen@hisilicon.com>,
        butao <butao@hisilicon.com>,
        "Xiaqing (A)" <saberlily.xia@hisilicon.com>,
        Yudongbin <yudongbin@hisilicon.com>,
        Chenbo Feng <fengc@google.com>,
        Alistair Strachan <astrachan@google.com>,
        dri-devel <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH v6 4/5] dma-buf: heaps: Add CMA heap to dmabuf heaps
Message-ID: <20190725124524.GB20286@infradead.org>
References: <20190624194908.121273-1-john.stultz@linaro.org>
 <20190624194908.121273-5-john.stultz@linaro.org>
 <20190718100840.GB19666@infradead.org>
 <CALAqxLWLx_tHVjZqrSNWfQ_M2RGGqh4qth3hi9GGRdSPov-gcw@mail.gmail.com>
 <20190724065958.GC16225@infradead.org>
 <CA+M3ks6yPTV4i=wEu41bHqMsn_VkYUj=y9BXGmgDgovnT9ESfA@mail.gmail.com>
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On Wed, Jul 24, 2019 at 10:08:54AM +0200, Benjamin Gaignard wrote:
> CMA has made possible to get large regions of memories and to give some
> priority on device allocating pages on it. I don't think that possible
> with system
> heap so I suggest to keep CMA heap if we want to be able to port a maximum
> of applications on dma-buf-heap.

Yes, CMA is a way to better allocate contigous regions, but it isn't
the only way to do that.

So at least for the system default CMA area it really should be a helper
for the system heap, especially given that CMA is an optional feature
and we can do high order contigous allocations using alloc_pages as
well.

Something like:

	if (!require_contigous && order > 0) {
		for (i = 0; i < nr_pages; i++)
			page[i] = alloc_page();
		goto done;
	} else if (order > 0)
		page = cma_alloc();
		if (page)
			goto done;
	}

	page = alloc_pages(order);