From: Christoph Hellwig <hch@lst.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Christoph Hellwig <hch@lst.de>,
Dave Hansen <dave.hansen@intel.com>,
Georgi Djakov <quic_c_gdjako@quicinc.com>,
catalin.marinas@arm.com, will@kernel.org,
dave.hansen@linux.intel.com, luto@kernel.org,
peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, m.szyprowski@samsung.com, robin.murphy@arm.com,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, djakov@kernel.org
Subject: Re: [RFC] mm: Allow ZONE_DMA32 to be disabled via kernel command line
Date: Fri, 27 Jan 2023 08:07:05 +0100 [thread overview]
Message-ID: <20230127070705.GA4180@lst.de> (raw)
In-Reply-To: <C7DCCCB1-AABE-4D3B-80B1-AB755A68D460@zytor.com>
On Thu, Jan 26, 2023 at 10:52:43PM -0800, H. Peter Anvin wrote:
> >If people want ZONE_DMA32 to go away we need something to replace
> >it first, like a large enough CMA region in the 32-bit addressable
> >range.
>
> Not to mention all kinds of odd masks like 30, 31, 39, 40, 46, ... bits.
Yes. Out of those all >= 32 are falling straight into ZONE_DM32,
the lower ones we do a first try in ZONE_DMA32 and then fall back to
ZONE_DMA. <= 29 mask OTOH are really rate in modern systems for
actual devices. So with a CMA region for what is currently ZONE_DMA
and one for the first 1G we'd probably cover most of what's actually
needed for x86_64. Of course on 32-bit architetures things become
a lot more complicated due to highmem.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Christoph Hellwig <hch@lst.de>,
Dave Hansen <dave.hansen@intel.com>,
Georgi Djakov <quic_c_gdjako@quicinc.com>,
catalin.marinas@arm.com, will@kernel.org,
dave.hansen@linux.intel.com, luto@kernel.org,
peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, m.szyprowski@samsung.com, robin.murphy@arm.com,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, djakov@kernel.org
Subject: Re: [RFC] mm: Allow ZONE_DMA32 to be disabled via kernel command line
Date: Fri, 27 Jan 2023 08:07:05 +0100 [thread overview]
Message-ID: <20230127070705.GA4180@lst.de> (raw)
In-Reply-To: <C7DCCCB1-AABE-4D3B-80B1-AB755A68D460@zytor.com>
On Thu, Jan 26, 2023 at 10:52:43PM -0800, H. Peter Anvin wrote:
> >If people want ZONE_DMA32 to go away we need something to replace
> >it first, like a large enough CMA region in the 32-bit addressable
> >range.
>
> Not to mention all kinds of odd masks like 30, 31, 39, 40, 46, ... bits.
Yes. Out of those all >= 32 are falling straight into ZONE_DM32,
the lower ones we do a first try in ZONE_DMA32 and then fall back to
ZONE_DMA. <= 29 mask OTOH are really rate in modern systems for
actual devices. So with a CMA region for what is currently ZONE_DMA
and one for the first 1G we'd probably cover most of what's actually
needed for x86_64. Of course on 32-bit architetures things become
a lot more complicated due to highmem.
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next prev parent reply other threads:[~2023-01-27 7:07 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-26 16:43 [RFC] mm: Allow ZONE_DMA32 to be disabled via kernel command line Georgi Djakov
2023-01-26 16:43 ` Georgi Djakov
2023-01-26 18:51 ` Dave Hansen
2023-01-26 18:51 ` Dave Hansen
2023-01-26 22:56 ` Georgi Djakov
2023-01-26 22:56 ` Georgi Djakov
2023-01-27 0:57 ` Randy Dunlap
2023-01-27 0:57 ` Randy Dunlap
2023-01-27 6:35 ` Christoph Hellwig
2023-01-27 6:35 ` Christoph Hellwig
2023-01-27 6:52 ` H. Peter Anvin
2023-01-27 6:52 ` H. Peter Anvin
2023-01-27 7:07 ` Christoph Hellwig [this message]
2023-01-27 7:07 ` Christoph Hellwig
2023-01-26 19:15 ` Robin Murphy
2023-01-26 19:15 ` Robin Murphy
2023-01-27 2:20 ` Chris Goldsworthy
2023-01-27 2:20 ` Chris Goldsworthy
2023-01-27 8:55 ` Hillf Danton
2023-01-27 8:55 ` Hillf Danton
2023-02-01 4:09 ` Chris Goldsworthy
2023-02-01 4:09 ` Chris Goldsworthy
2023-01-30 5:26 ` kernel test robot
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