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From: Florian Fainelli <f.fainelli@gmail.com>
To: Rob Herring <robh@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>, Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Olof Johansson <olof@lixom.net>,
	linux-alpha@vger.kernel.org,
	arcml <linux-snps-arc@lists.infradead.org>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
	<linux-arm-kernel@lists.infradead.org>,
	linux-c6x-dev@linux-c6x.org,
	"moderated list:H8/300 ARCHITECTURE" 
	<uclinux-h8-devel@lists.sourceforge.jp>,
	linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org,
	Linux-MIPS <linux-mips@linux-mips.org>,
	nios2-dev@lists.rocketboards.org,
	Openrisc <openrisc@lists.librecores.org>,
	linux-parisc@vger.kernel.org,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
	SH-Linux <linux-sh@vger.kernel.org>,
	sparclinux@vger.kernel.org, linux-um@lists.infradead.org,
	linux-xtensa@linux-xtensa.org, devicetree@vger.kernel.org,
	"open list:GENERIC INCLUDE/ASM HEADER FILES" 
	<linux-arch@vger.kernel.org>
Subject: Re: [PATCH v2 0/2] arm64: Cut rebuild time when changing CONFIG_BLK_DEV_INITRD
Date: Wed, 24 Oct 2018 13:01:19 -0700	[thread overview]
Message-ID: <6e647f76-8523-09d3-9b72-d8d8abd213a4@gmail.com> (raw)
In-Reply-To: <CAL_Jsq+KCOv6pXXHhHDZ+7-QUrmtMDvSjEVhK15yZ3qbnn61Ag@mail.gmail.com>

On 10/24/18 12:55 PM, Rob Herring wrote:
> On Wed, Oct 24, 2018 at 2:33 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
>>
>> Hi all,
>>
>> While investigating why ARM64 required a ton of objects to be rebuilt
>> when toggling CONFIG_DEV_BLK_INITRD, it became clear that this was
>> because we define __early_init_dt_declare_initrd() differently and we do
>> that in arch/arm64/include/asm/memory.h which gets included by a fair
>> amount of other header files, and translation units as well.
> 
> I scratch my head sometimes as to why some config options rebuild so
> much stuff. One down, ? to go. :)
> 

This one was by far the most invasive one due to its include chain, but
yes, there would be many more that could be optimized.

>> Changing the value of CONFIG_DEV_BLK_INITRD is a common thing with build
>> systems that generate two kernels: one with the initramfs and one
>> without. buildroot is one of these build systems, OpenWrt is also
>> another one that does this.
>>
>> This patch series proposes adding an empty initrd.h to satisfy the need
>> for drivers/of/fdt.c to unconditionally include that file, and moves the
>> custom __early_init_dt_declare_initrd() definition away from
>> asm/memory.h
>>
>> This cuts the number of objects rebuilds from 1920 down to 26, so a
>> factor 73 approximately.
>>
>> Apologies for the long CC list, please let me know how you would go
>> about merging that and if another approach would be preferable, e.g:
>> introducing a CONFIG_ARCH_INITRD_BELOW_START_OK Kconfig option or
>> something like that.
> 
> There may be a better way as of 4.20 because bootmem is now gone and
> only memblock is used. This should unify what each arch needs to do
> with initrd early. We need the physical address early for memblock
> reserving. Then later on we need the virtual address to access the
> initrd. Perhaps we should just change initrd_start and initrd_end to
> physical addresses (or add 2 new variables would be less invasive and
> allow for different translation than __va()). The sanity checks and
> memblock reserve could also perhaps be moved to a common location.
> 
> Alternatively, given arm64 is the only oddball, I'd be fine with an
> "if (IS_ENABLED(CONFIG_ARM64))" condition in the default
> __early_init_dt_declare_initrd as long as we have a path to removing
> it like the above option.

OK, let me cook a patch doing that and meanwhile I will look at how much
work is involved to implement the above option you outlined, which also
sounds entirely reasonable.

Thanks!
-- 
Florian

  reply	other threads:[~2018-10-24 20:01 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-24 19:32 Florian Fainelli
2018-10-24 19:32 ` [PATCH v2 1/2] arch: Add asm-generic/initrd.h and make use of it for most architectures Florian Fainelli
2018-10-24 19:32 ` [PATCH v2 2/2] arm64: Create asm/initrd.h Florian Fainelli
2018-10-24 19:55 ` [PATCH v2 0/2] arm64: Cut rebuild time when changing CONFIG_BLK_DEV_INITRD Rob Herring
2018-10-24 20:01   ` Florian Fainelli [this message]
2018-10-24 21:25     ` Rob Herring
2018-10-25  9:38   ` Mike Rapoport
2018-10-25  9:51     ` Russell King - ARM Linux
2018-10-25 13:15     ` Rob Herring
2018-10-25 17:29       ` Mike Rapoport
2018-10-25 21:13         ` Rob Herring
2018-10-25 23:07           ` Florian Fainelli
2018-10-26 11:07             ` Mike Rapoport
2018-10-26 19:05               ` Florian Fainelli
2018-10-26  8:12           ` Mike Rapoport

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