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From: Catalin Marinas <catalin.marinas@arm.com>
To: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
	Linux kernel mailing list <linux-kernel@vger.kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [arm64] kernel boot slowdown in v5.10.19 -> v5.10.42 update
Date: Fri, 28 Jan 2022 12:06:15 +0000	[thread overview]
Message-ID: <YfPcNy3JcnwuJNMx@arm.com> (raw)
In-Reply-To: <9a34ee9b-0ede-30a6-0898-d32fe81d5b0c@linux.microsoft.com>

On Mon, Jan 24, 2022 at 03:03:48PM -0800, Vijay Balakrishna wrote:
> We noticed 150ms kernel boot slowdown back in June, 2021, when moving from
> v5.10.19 to v5.10.42.  This on a 8GB SoC.  Only recently we investigated
> this issue and found the regression is introduced by a change in map_mem()
> (paging_init() -> map_mem() -> __map_memblock(), in particular "map all the
> memory banks" for loop) by patch
> 
> 2687275a5843d1089687f08fc64eb3f3b026a169
> arm64: Force NO_BLOCK_MAPPINGS if crashkernel reservation is required
> 
> above is a follow up to
> 
> 0a30c53573b07d5561457e41fb0ab046cd857da5
> arm64: mm: Move reserve_crashkernel() into mem_init())
> 
> which deferred crashkernel reservation into mem_init().
> 
> The ~150ms slowdown disappears on booting without "crashkernel=.." on kernel
> command-line.

Is CONFIG_RODATA_FULL_DEFAULT_ENABLED set in your config file? It may
cause the same slowdown. I suspect it's because we end up mapping the
RAM at the page granularity so more loops and slightly higher TLB
pressure. Not sure we can do much about.

-- 
Catalin

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
	Linux kernel mailing list <linux-kernel@vger.kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [arm64] kernel boot slowdown in v5.10.19 -> v5.10.42 update
Date: Fri, 28 Jan 2022 12:06:15 +0000	[thread overview]
Message-ID: <YfPcNy3JcnwuJNMx@arm.com> (raw)
In-Reply-To: <9a34ee9b-0ede-30a6-0898-d32fe81d5b0c@linux.microsoft.com>

On Mon, Jan 24, 2022 at 03:03:48PM -0800, Vijay Balakrishna wrote:
> We noticed 150ms kernel boot slowdown back in June, 2021, when moving from
> v5.10.19 to v5.10.42.  This on a 8GB SoC.  Only recently we investigated
> this issue and found the regression is introduced by a change in map_mem()
> (paging_init() -> map_mem() -> __map_memblock(), in particular "map all the
> memory banks" for loop) by patch
> 
> 2687275a5843d1089687f08fc64eb3f3b026a169
> arm64: Force NO_BLOCK_MAPPINGS if crashkernel reservation is required
> 
> above is a follow up to
> 
> 0a30c53573b07d5561457e41fb0ab046cd857da5
> arm64: mm: Move reserve_crashkernel() into mem_init())
> 
> which deferred crashkernel reservation into mem_init().
> 
> The ~150ms slowdown disappears on booting without "crashkernel=.." on kernel
> command-line.

Is CONFIG_RODATA_FULL_DEFAULT_ENABLED set in your config file? It may
cause the same slowdown. I suspect it's because we end up mapping the
RAM at the page granularity so more loops and slightly higher TLB
pressure. Not sure we can do much about.

-- 
Catalin

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-01-28 12:06 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-24 23:03 [arm64] kernel boot slowdown in v5.10.19 -> v5.10.42 update Vijay Balakrishna
2022-01-24 23:03 ` Vijay Balakrishna
2022-01-28 12:06 ` Catalin Marinas [this message]
2022-01-28 12:06   ` Catalin Marinas
2022-01-28 18:03   ` Vijay Balakrishna
2022-01-28 18:03     ` Vijay Balakrishna
2022-02-09 21:47     ` Vijay Balakrishna
2022-02-09 21:47       ` Vijay Balakrishna

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