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From: "Vaneet Narang" <v.narang@samsung.com>
To: "Russell King - ARM Linux" <linux@armlinux.org.uk>,
	"Maninder Singh" <maninder1.s@samsung.com>
Cc: "nicolas.pitre@linaro.org" <nicolas.pitre@linaro.org>,
	"ssantosh@kernel.org" <ssantosh@kernel.org>,
	"panand@redhat.com" <panand@redhat.com>,
	"arnd@arndb.de" <arnd@arndb.de>,
	"chris.brandt@renesas.com" <chris.brandt@renesas.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"PANKAJ MISHRA" <pankaj.m@samsung.com>,
	"Ajeet Kumar Yadav" <ajeet.y@samsung.com>
Subject: RE: Re: [PATCH 1/1] arm/module: maximum utilization of module area.
Date: Mon, 12 Dec 2016 11:22:30 +0000	[thread overview]
Message-ID: <20161212112230epcms5p6af05aef34f72eab15061a166d18cff00@epcms5p6> (raw)
In-Reply-To: <CGME20161212102403epcas4p2e039072e2acdc3d20c1b8ac86e823375@epcas4p2.samsung.com>

[-- Attachment #1: Type: text/plain, Size: 1307 bytes --]

Hi,

>A PC24 relocation has a range of +/-32MB.  This means that where-ever
>the module is placed, it must be capable of reaching any function
>within the kernel text, which may itself be quite large (eg, 8MB, or
>possibly larger).  The module area exists to allow modules to be
>located in an area where PC24 relocations are able to reach all of the
>kernel text on sensibly configured kernels, thereby allowing for
>optimal performance.
>
>If you wish to load large modules, then enable ARM_MODULE_PLTS, which
>will use the less efficient PLT method (which is basically an indirect
>function call) for relocations that PC24 can't handle, and will allow
>the module to be loaded into the vmalloc area.
>
>Growing the module area so that smaller modules also get penalised by
>the PLT indirection is not sane.

This is exactly what i am saying. These changes are useful to accomdate
22MB modules without enabling ARM_MODULE_PLTS. 
Without these changes ARM_MODULE_PLTS needs to be enabled to insert more than 14MB
modules but with these changes 22MB modules (considering 8MB uImage) can be inserted 
without enabling ARM_MODULE_PLTS.

So till 22MB modules are not penalised but without these changes once size of modules
gets over 14MB PLT becomes must. 

Regards,
Vaneet Narang

  parent reply	other threads:[~2016-12-12 12:05 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-06  8:29 Maninder Singh
2016-12-06  9:13 ` Ard Biesheuvel
2016-12-06 15:57 ` Nicolas Pitre
     [not found] ` <CGME20161206091317epcas3p3702de092ecce4ac079b27180dd48c744@epcas3p3.samsung.com>
2016-12-12 10:08   ` Vaneet Narang
2016-12-12 10:23 ` Russell King - ARM Linux
     [not found] ` <CGME20161212102403epcas4p2e039072e2acdc3d20c1b8ac86e823375@epcas4p2.samsung.com>
2016-12-12 11:22   ` Vaneet Narang [this message]
2016-12-12 12:56     ` Russell King - ARM Linux
2016-12-12 15:28     ` Nicolas Pitre
2016-12-12 16:57       ` Ard Biesheuvel

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