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Message-ID: <3a530804ad5aa96d2502da8ee3e8650b0b477c0f.camel@suse.de>
Subject: Re: [PATCH v2 2/2] dma-pool: Only allocate from CMA when in same
 memory zone
From:   Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To:     Christoph Hellwig <hch@lst.de>
Cc:     amit.pundir@linaro.org, linux-kernel@vger.kernel.org,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>, rientjes@google.com,
        jeremy.linton@arm.com, linux-rpi-kernel@lists.infradead.org,
        iommu@lists.linux-foundation.org
Date:   Thu, 06 Aug 2020 13:50:29 +0200
In-Reply-To: <20200806051814.GA10143@lst.de>
References: <20200803160956.19235-1-nsaenzjulienne@suse.de>
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On Thu, 2020-08-06 at 07:18 +0200, Christoph Hellwig wrote:
> On Tue, Aug 04, 2020 at 11:43:15AM +0200, Nicolas Saenz Julienne wrote:
> > > Second I don't see the need (and actually some harm) in preventing GF=
P_KERNEL
> > > allocations from dipping into lower CMA areas - something that we did=
 support
> > > before 5.8 with the single pool.
> >=20
> > My thinking is the least we pressure CMA the better, it's generally sca=
rse, and
> > it'll not grow as the atomic pools grow. As far as harm is concerned, w=
e now
> > check addresses for correctness, so we shouldn't run into problems.
> >=20
> > There is a potential case for architectures defining a default CMA but =
not
> > defining DMA zones where this could be problematic. But isn't that just=
 plain
> > abusing CMA? If you need low memory allocations, you should be defining=
 DMA
> > zones.
>=20
> The latter is pretty much what I expect, as we only support the default a=
nd
> per-device DMA CMAs.

Fair enough, should I send a v3 with everything cleaned-up/rebased, or you'=
d
rather pick it up from your version?


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