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From: Catalin Marinas <catalin.marinas@arm.com>
To: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: jmorris@namei.org, sashal@kernel.org, ebiederm@xmission.com,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	corbet@lwn.net, will@kernel.org,
	linux-arm-kernel@lists.infradead.org, maz@kernel.org,
	james.morse@arm.com, vladimir.murzin@arm.com,
	matthias.bgg@gmail.com, linux-mm@kvack.org, mark.rutland@arm.com,
	steve.capper@arm.com, rfontana@redhat.com, tglx@linutronix.de,
	selindag@gmail.com, tyhicks@linux.microsoft.com,
	kernelfans@gmail.com, akpm@linux-foundation.org,
	madvenka@linux.microsoft.com
Subject: Re: [PATCH v16 00/15] arm64: MMU enabled kexec relocation
Date: Tue, 24 Aug 2021 19:05:56 +0100	[thread overview]
Message-ID: <20210824180555.GD623@arm.com> (raw)
In-Reply-To: <20210802215408.804942-1-pasha.tatashin@soleen.com>

Hi Pavel,

This series is still missing reviews from those who understand kexec
better than me.

On Mon, Aug 02, 2021 at 05:53:53PM -0400, Pavel Tatashin wrote:
> Enable MMU during kexec relocation in order to improve reboot performance.
> 
> If kexec functionality is used for a fast system update, with a minimal
> downtime, the relocation of kernel + initramfs takes a significant portion
> of reboot.
> 
> The reason for slow relocation is because it is done without MMU, and thus
> not benefiting from D-Cache.

The performance improvements are indeed significant on some platforms
(going from 7s to ~40ms), so I think the merging the series is worth it.
Some general questions so I better understand the impact:

- Is the kdump path affected in any way? IIUC that doesn't need any
  relocation but we should also make sure we don't create the additional
  page table unnecessarily (should keep as much memory intact as
  possible). Maybe that's already handled.

- What happens if trans_pgd_create_copy() fails to allocate memory. Does
  it fall back to an MMU-off relocation?

And I presume this series does not introduce any changes to the kexec
tools ABI.

Thanks.

-- 
Catalin

  parent reply	other threads:[~2021-08-24 18:06 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-02 21:53 Pavel Tatashin
2021-08-02 21:53 ` [PATCH v16 01/15] arm64: kernel: add helper for booted at EL2 and not VHE Pavel Tatashin
2021-08-02 21:53 ` [PATCH v16 02/15] arm64: trans_pgd: hibernate: Add trans_pgd_copy_el2_vectors Pavel Tatashin
2021-08-02 21:53 ` [PATCH v16 03/15] arm64: hibernate: abstract ttrb0 setup function Pavel Tatashin
2021-08-02 21:53 ` [PATCH v16 04/15] arm64: kexec: flush image and lists during kexec load time Pavel Tatashin
2021-08-02 21:53 ` [PATCH v16 05/15] arm64: kexec: skip relocation code for inplace kexec Pavel Tatashin
2021-08-02 21:53 ` [PATCH v16 06/15] arm64: kexec: Use dcache ops macros instead of open-coding Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 07/15] arm64: kexec: pass kimage as the only argument to relocation function Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 08/15] arm64: kexec: configure EL2 vectors for kexec Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 09/15] arm64: kexec: relocate in EL1 mode Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 10/15] arm64: kexec: use ld script for relocation function Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 11/15] arm64: kexec: install a copy of the linear-map Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 12/15] arm64: kexec: keep MMU enabled during kexec relocation Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 13/15] arm64: kexec: remove the pre-kexec PoC maintenance Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 14/15] arm64: kexec: remove cpu-reset.h Pavel Tatashin
2021-08-02 21:54 ` [PATCH v16 15/15] arm64: trans_pgd: remove trans_pgd_map_page() Pavel Tatashin
2021-08-24 18:05 ` Catalin Marinas [this message]
2021-08-26 15:03   ` [PATCH v16 00/15] arm64: MMU enabled kexec relocation Pavel Tatashin
2021-09-16  9:37     ` Catalin Marinas
2021-09-16 22:32       ` Pasha Tatashin
2021-09-08  8:59 ` Pingfan Liu

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