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
Subject: Re: [PATCH v2 2/2] dma-pool: Only allocate from CMA when in same memory zone
Date: Thu, 06 Aug 2020 13:50:29 +0200 [thread overview]
Message-ID: <3a530804ad5aa96d2502da8ee3e8650b0b477c0f.camel@suse.de> (raw)
In-Reply-To: <20200806051814.GA10143@lst.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 GFP_KERNEL
> > > allocations from dipping into lower CMA areas - something that we did support
> > > before 5.8 with the single pool.
> >
> > My thinking is the least we pressure CMA the better, it's generally scarse, and
> > it'll not grow as the atomic pools grow. As far as harm is concerned, we now
> > check addresses for correctness, so we shouldn't run into problems.
> >
> > 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.
>
> The latter is pretty much what I expect, as we only support the default and
> 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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From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: amit.pundir@linaro.org, linux-kernel@vger.kernel.org,
jeremy.linton@arm.com, iommu@lists.linux-foundation.org,
linux-rpi-kernel@lists.infradead.org, rientjes@google.com,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v2 2/2] dma-pool: Only allocate from CMA when in same memory zone
Date: Thu, 06 Aug 2020 13:50:29 +0200 [thread overview]
Message-ID: <3a530804ad5aa96d2502da8ee3e8650b0b477c0f.camel@suse.de> (raw)
In-Reply-To: <20200806051814.GA10143@lst.de>
[-- Attachment #1.1: Type: text/plain, Size: 1081 bytes --]
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 GFP_KERNEL
> > > allocations from dipping into lower CMA areas - something that we did support
> > > before 5.8 with the single pool.
> >
> > My thinking is the least we pressure CMA the better, it's generally scarse, and
> > it'll not grow as the atomic pools grow. As far as harm is concerned, we now
> > check addresses for correctness, so we shouldn't run into problems.
> >
> > 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.
>
> The latter is pretty much what I expect, as we only support the default and
> 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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next prev parent reply other threads:[~2020-08-06 17:23 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 16:09 [PATCH v2 0/2] dma-pool fixes Nicolas Saenz Julienne
2020-08-03 16:09 ` Nicolas Saenz Julienne
2020-08-03 16:09 ` [PATCH v2 1/2] dma-pool: fix coherent pool allocations for IOMMU mappings Nicolas Saenz Julienne
2020-08-03 16:09 ` Nicolas Saenz Julienne
2020-08-03 16:09 ` [PATCH v2 2/2] dma-pool: Only allocate from CMA when in same memory zone Nicolas Saenz Julienne
2020-08-03 16:09 ` Nicolas Saenz Julienne
2020-08-04 6:06 ` Christoph Hellwig
2020-08-04 6:06 ` Christoph Hellwig
2020-08-04 9:43 ` Nicolas Saenz Julienne
2020-08-04 9:43 ` Nicolas Saenz Julienne
2020-08-06 5:18 ` Christoph Hellwig
2020-08-06 5:18 ` Christoph Hellwig
2020-08-06 11:50 ` Nicolas Saenz Julienne [this message]
2020-08-06 11:50 ` Nicolas Saenz Julienne
2020-08-06 13:55 ` Christoph Hellwig
2020-08-06 13:55 ` Christoph Hellwig
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