From: Will Deacon <will@kernel.org>
To: Guanghui Feng <guanghuifeng@linux.alibaba.com>
Cc: baolin.wang@linux.alibaba.com, catalin.marinas@arm.com,
akpm@linux-foundation.org, david@redhat.com, jianyong.wu@arm.com,
james.morse@arm.com, quic_qiancai@quicinc.com,
christophe.leroy@csgroup.eu, jonathan@marek.ca,
mark.rutland@arm.com, thunder.leizhen@huawei.com,
anshuman.khandual@arm.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, rppt@kernel.org,
geert+renesas@glider.be, ardb@kernel.org, linux-mm@kvack.org,
yaohongbo@linux.alibaba.com,
alikernel-developer@linux.alibaba.com
Subject: Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation
Date: Mon, 4 Jul 2022 11:35:23 +0100 [thread overview]
Message-ID: <20220704103523.GC31437@willie-the-truck> (raw)
In-Reply-To: <1656777473-73887-1-git-send-email-guanghuifeng@linux.alibaba.com>
On Sat, Jul 02, 2022 at 11:57:53PM +0800, Guanghui Feng wrote:
> The arm64 can build 2M/1G block/sectiion mapping. When using DMA/DMA32 zone
> (enable crashkernel, disable rodata full, disable kfence), the mem_map will
> use non block/section mapping(for crashkernel requires to shrink the region
> in page granularity). But it will degrade performance when doing larging
> continuous mem access in kernel(memcpy/memmove, etc).
Hmm. It seems a bit silly to me that we take special care to unmap the
crashkernel from the linear map even when can_set_direct_map() is false, as
we won't be protecting the main kernel at all!
Why don't we just leave the crashkernel mapped if !can_set_direct_map()
and then this problem just goes away?
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: Guanghui Feng <guanghuifeng@linux.alibaba.com>
Cc: baolin.wang@linux.alibaba.com, catalin.marinas@arm.com,
akpm@linux-foundation.org, david@redhat.com, jianyong.wu@arm.com,
james.morse@arm.com, quic_qiancai@quicinc.com,
christophe.leroy@csgroup.eu, jonathan@marek.ca,
mark.rutland@arm.com, thunder.leizhen@huawei.com,
anshuman.khandual@arm.com, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, rppt@kernel.org,
geert+renesas@glider.be, ardb@kernel.org, linux-mm@kvack.org,
yaohongbo@linux.alibaba.com,
alikernel-developer@linux.alibaba.com
Subject: Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation
Date: Mon, 4 Jul 2022 11:35:23 +0100 [thread overview]
Message-ID: <20220704103523.GC31437@willie-the-truck> (raw)
In-Reply-To: <1656777473-73887-1-git-send-email-guanghuifeng@linux.alibaba.com>
On Sat, Jul 02, 2022 at 11:57:53PM +0800, Guanghui Feng wrote:
> The arm64 can build 2M/1G block/sectiion mapping. When using DMA/DMA32 zone
> (enable crashkernel, disable rodata full, disable kfence), the mem_map will
> use non block/section mapping(for crashkernel requires to shrink the region
> in page granularity). But it will degrade performance when doing larging
> continuous mem access in kernel(memcpy/memmove, etc).
Hmm. It seems a bit silly to me that we take special care to unmap the
crashkernel from the linear map even when can_set_direct_map() is false, as
we won't be protecting the main kernel at all!
Why don't we just leave the crashkernel mapped if !can_set_direct_map()
and then this problem just goes away?
Will
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-07-04 10:35 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-02 15:57 [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation Guanghui Feng
2022-07-02 15:57 ` Guanghui Feng
2022-07-04 10:35 ` Will Deacon [this message]
2022-07-04 10:35 ` Will Deacon
2022-07-04 10:58 ` guanghui.fgh
2022-07-04 10:58 ` guanghui.fgh
2022-07-04 11:14 ` Will Deacon
2022-07-04 11:14 ` Will Deacon
2022-07-04 12:05 ` guanghui.fgh
2022-07-04 12:05 ` guanghui.fgh
2022-07-04 13:15 ` Will Deacon
2022-07-04 13:15 ` Will Deacon
2022-07-04 13:41 ` guanghui.fgh
2022-07-04 13:41 ` guanghui.fgh
2022-07-04 14:11 ` guanghui.fgh
2022-07-04 14:11 ` guanghui.fgh
2022-07-04 14:23 ` Will Deacon
2022-07-04 14:23 ` Will Deacon
2022-07-04 14:34 ` guanghui.fgh
2022-07-04 14:34 ` guanghui.fgh
2022-07-04 16:38 ` Will Deacon
2022-07-04 16:38 ` Will Deacon
2022-07-04 17:09 ` Ard Biesheuvel
2022-07-04 17:09 ` Ard Biesheuvel
2022-07-05 8:35 ` Baoquan He
2022-07-05 8:35 ` Baoquan He
2022-07-05 8:35 ` Baoquan He
2022-07-05 9:52 ` Will Deacon
2022-07-05 9:52 ` Will Deacon
2022-07-05 12:07 ` guanghui.fgh
2022-07-05 12:07 ` guanghui.fgh
2022-07-05 12:11 ` Will Deacon
2022-07-05 12:11 ` Will Deacon
2022-07-05 12:27 ` guanghui.fgh
2022-07-05 12:27 ` guanghui.fgh
2022-07-05 12:56 ` Mike Rapoport
2022-07-05 12:56 ` Mike Rapoport
2022-07-05 13:17 ` guanghui.fgh
2022-07-05 13:17 ` guanghui.fgh
2022-07-05 15:02 ` Mike Rapoport
2022-07-05 15:02 ` Mike Rapoport
2022-07-05 15:34 ` Catalin Marinas
2022-07-05 15:34 ` Catalin Marinas
2022-07-05 15:57 ` Mike Rapoport
2022-07-05 15:57 ` Mike Rapoport
2022-07-05 17:05 ` Catalin Marinas
2022-07-05 17:05 ` Catalin Marinas
2022-07-05 20:45 ` Mike Rapoport
2022-07-05 20:45 ` Mike Rapoport
2022-07-06 2:49 ` guanghui.fgh
2022-07-06 2:49 ` guanghui.fgh
2022-07-06 7:43 ` Catalin Marinas
2022-07-06 7:43 ` Catalin Marinas
2022-07-06 10:04 ` Catalin Marinas
2022-07-06 10:04 ` Catalin Marinas
2022-07-06 13:54 ` Mike Rapoport
2022-07-06 13:54 ` Mike Rapoport
2022-07-06 15:18 ` guanghui.fgh
2022-07-06 15:18 ` guanghui.fgh
2022-07-06 15:30 ` guanghui.fgh
2022-07-06 15:30 ` guanghui.fgh
2022-07-06 15:40 ` Catalin Marinas
2022-07-06 15:40 ` Catalin Marinas
2022-07-07 17:02 ` guanghui.fgh
2022-07-07 17:02 ` guanghui.fgh
2022-07-08 12:28 ` [PATCH RESEND " guanghui.fgh
2022-07-08 12:28 ` guanghui.fgh
2022-07-10 13:44 ` [PATCH v5] " Guanghui Feng
2022-07-10 13:44 ` Guanghui Feng
2022-07-10 14:32 ` guanghui.fgh
2022-07-10 14:32 ` guanghui.fgh
2022-07-10 15:33 ` guanghui.fgh
2022-07-10 15:33 ` guanghui.fgh
2022-07-18 13:10 ` Will Deacon
2022-07-18 13:10 ` Will Deacon
2022-07-25 6:46 ` Mike Rapoport
2022-07-25 6:46 ` Mike Rapoport
2022-07-05 2:44 ` [PATCH v4] " guanghui.fgh
2022-07-05 2:44 ` guanghui.fgh
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