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From: Nicolin Chen <nicoleotsuka@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: robin.murphy@arm.com, vdumpa@nvidia.com, linux@armlinux.org.uk,
	catalin.marinas@arm.com, will.deacon@arm.com, joro@8bytes.org,
	m.szyprowski@samsung.com, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	tony@atomide.com
Subject: Re: [PATCH v2 RFC/RFT 0/5] Save single pages from CMA area
Date: Wed, 27 Mar 2019 11:42:32 -0700	[thread overview]
Message-ID: <20190327184231.GA13287@Asurada-Nvidia> (raw)
In-Reply-To: <20190327080821.GB20336@lst.de>

On Wed, Mar 27, 2019 at 09:08:21AM +0100, Christoph Hellwig wrote:
> On Tue, Mar 26, 2019 at 04:01:26PM -0700, Nicolin Chen wrote:
> > This series of patches try to save single pages from CMA area bypassing
> > all CMA single page alloctions and allocating normal pages instead, as
> > all addresses within one single page are contiguous.
> > 
> > We had once applied the PATCH-5 but reverted it as actually not all the
> > callers handled the fallback allocations. Per Robin's suggestion, let's
> > stuff alloc_pages()/free_page() fallbacks to those callers before having
> > PATCH-5.
> 
> Given the problems this has caused so far I'd like to see a good
> explanation of why this optimization is so important that all the churn
> is even worth it..

With certain downstream user cases, we had run into a CMA exhaustion
situation, and this was one of the changes that eased the problem. I
have all the reasoning in the PATCH-5 commit message. And what Robin
tested can also justify for it:
https://lore.kernel.org/patchwork/patch/1004934/#1190139

Thanks

WARNING: multiple messages have this Message-ID (diff)
From: Nicolin Chen <nicoleotsuka@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: tony@atomide.com, catalin.marinas@arm.com, joro@8bytes.org,
	will.deacon@arm.com, linux@armlinux.org.uk,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org,
	m.szyprowski@samsung.com
Subject: Re: [PATCH v2 RFC/RFT 0/5] Save single pages from CMA area
Date: Wed, 27 Mar 2019 11:42:32 -0700	[thread overview]
Message-ID: <20190327184231.GA13287@Asurada-Nvidia> (raw)
In-Reply-To: <20190327080821.GB20336@lst.de>

On Wed, Mar 27, 2019 at 09:08:21AM +0100, Christoph Hellwig wrote:
> On Tue, Mar 26, 2019 at 04:01:26PM -0700, Nicolin Chen wrote:
> > This series of patches try to save single pages from CMA area bypassing
> > all CMA single page alloctions and allocating normal pages instead, as
> > all addresses within one single page are contiguous.
> > 
> > We had once applied the PATCH-5 but reverted it as actually not all the
> > callers handled the fallback allocations. Per Robin's suggestion, let's
> > stuff alloc_pages()/free_page() fallbacks to those callers before having
> > PATCH-5.
> 
> Given the problems this has caused so far I'd like to see a good
> explanation of why this optimization is so important that all the churn
> is even worth it..

With certain downstream user cases, we had run into a CMA exhaustion
situation, and this was one of the changes that eased the problem. I
have all the reasoning in the PATCH-5 commit message. And what Robin
tested can also justify for it:
https://lore.kernel.org/patchwork/patch/1004934/#1190139

Thanks

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linux-arm-kernel@lists.infradead.org
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  reply	other threads:[~2019-03-27 18:42 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-26 23:01 [PATCH v2 RFC/RFT 0/5] Save single pages from CMA area Nicolin Chen
2019-03-26 23:01 ` Nicolin Chen
     [not found] ` <20190326230131.16275-1-nicoleotsuka-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2019-03-26 23:01   ` [PATCH v2 RFC/RFT 1/5] ARM: dma-mapping: Add fallback normal page allocations Nicolin Chen
2019-03-26 23:01     ` Nicolin Chen
2019-03-26 23:01     ` Nicolin Chen
2019-04-24 15:06     ` Christoph Hellwig
2019-04-24 15:06       ` Christoph Hellwig
2019-04-24 15:06       ` Christoph Hellwig
     [not found]       ` <20190424150638.GA22191-jcswGhMUV9g@public.gmane.org>
2019-04-24 15:08         ` Christoph Hellwig
2019-04-24 15:08           ` Christoph Hellwig
2019-04-24 15:08           ` Christoph Hellwig
2019-04-24 15:08           ` Christoph Hellwig
2019-04-24 18:33       ` Nicolin Chen
2019-04-24 18:33         ` Nicolin Chen
2019-04-24 18:33         ` Nicolin Chen
2019-04-24 19:26         ` Christoph Hellwig
2019-04-24 19:26           ` Christoph Hellwig
2019-04-24 19:26           ` Christoph Hellwig
2019-04-24 19:38           ` Nicolin Chen
2019-04-24 19:38             ` Nicolin Chen
2019-04-24 19:38             ` Nicolin Chen
2019-04-30 15:24           ` Catalin Marinas
2019-04-30 15:24             ` Catalin Marinas
2019-04-30 15:24             ` Catalin Marinas
2019-05-02 13:26             ` Christoph Hellwig
2019-05-02 13:26               ` Christoph Hellwig
2019-05-02 13:26               ` Christoph Hellwig
2019-05-02 13:26               ` Christoph Hellwig
2019-04-26 20:21       ` Nicolin Chen
2019-04-26 20:21         ` Nicolin Chen
2019-04-26 20:21         ` Nicolin Chen
2019-04-26 20:25         ` Christoph Hellwig
2019-04-26 20:25           ` Christoph Hellwig
2019-04-26 20:25           ` Christoph Hellwig
2019-03-26 23:01   ` [PATCH v2 RFC/RFT 2/5] dma-remap: Run alloc_pages() on failure Nicolin Chen
2019-03-26 23:01     ` Nicolin Chen
2019-03-26 23:01     ` Nicolin Chen
2019-03-26 23:01 ` [PATCH v2 RFC/RFT 3/5] iommu: amd_iommu: Add fallback normal page allocations Nicolin Chen
2019-03-26 23:01   ` Nicolin Chen
2019-03-26 23:01 ` [PATCH v2 RFC/RFT 4/5] arm64: dma-mapping: " Nicolin Chen
2019-03-26 23:01   ` Nicolin Chen
2019-03-26 23:01 ` [PATCH v2 RFC/RFT 5/5] dma-contiguous: Do not allocate a single page from CMA area Nicolin Chen
2019-03-26 23:01   ` Nicolin Chen
2019-03-27  8:08 ` [PATCH v2 RFC/RFT 0/5] Save single pages " Christoph Hellwig
2019-03-27  8:08   ` Christoph Hellwig
2019-03-27 18:42   ` Nicolin Chen [this message]
2019-03-27 18:42     ` Nicolin Chen

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