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From: Matthias Maennich <maennich@google.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org, kernel-team@android.com,
	Jessica Yu <jeyu@kernel.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Martijn Coenen <maco@android.com>,
	Lucas De Marchi <lucas.de.marchi@gmail.com>,
	Shaun Ruffell <sruffell@sruffell.net>,
	Will Deacon <will@kernel.org>,
	linux-kbuild@vger.kernel.org, linux-modules@vger.kernel.org,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: Re: [PATCH 4/4] export: avoid code duplication in include/linux/export.h
Date: Fri, 11 Oct 2019 16:43:11 +0100
Message-ID: <20191011154311.GA192647@google.com> (raw)
In-Reply-To: <20191011153127.GA1283883@kroah.com>

On Fri, Oct 11, 2019 at 05:31:27PM +0200, Greg Kroah-Hartman wrote:
>On Thu, Oct 10, 2019 at 04:14:43PM +0100, Matthias Maennich wrote:
>> Now that the namespace value is not part of the __ksymtab entry name
>> anymore, we can simplify the implementation of EXPORT_SYMBOL*. By
>> allowing the empty string "" to represent 'no namespace', we can unify
>> the implementation and drop a lot redundant code.  That increases
>> readability and maintainability.
>>
>> As Masahiro pointed out earlier,
>> "The drawback of this change is, it grows the code size. When the symbol
>> has no namespace, sym->namespace was previously NULL, but it is now am
>> empty string "". So, it increases 1 byte for every no namespace
>> EXPORT_SYMBOL. A typical kernel configuration has 10K exported symbols,
>> so it increases 10KB in rough estimation."
>
>10Kb of non-swapable memory isn't good.  But if you care about that, you
>can get it back with the option to compile away any non-used symbols,
>and that shouldn't be affected by this change, right?

Rasmus suggested to put the 'aMS' flags on the __ksymtab_strings section
to mitigate this:
https://lore.kernel.org/lkml/f2e28d6b-77c5-5fe2-0bc4-b24955de9954@rasmusvillemoes.dk/

I was not yet able to properly test this, so I did not include it in
this series. As I said in the cover letter, this 4th patch might be
optional for 5.4. So, we could defer it to a later time when we have
addressed that properly.

Cheers,
Matthias

>
>That being said, the code is a lot cleaner, so I have no objection to
>it.
>
>Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-10 15:14 [PATCH 0/4] export/modpost: avoid renaming __ksymtab entries for symbol namespaces Matthias Maennich
2019-10-10 15:14 ` [PATCH 1/4] modpost: delegate updating namespaces to separate function Matthias Maennich
2019-10-11 14:24   ` Will Deacon
2019-10-11 15:32   ` Greg Kroah-Hartman
2019-10-12  3:19     ` Masahiro Yamada
2019-10-10 15:14 ` [PATCH 2/4] modpost: make updating the symbol namespace explict Matthias Maennich
2019-10-11 14:24   ` Will Deacon
2019-10-11 15:33   ` Greg Kroah-Hartman
2019-10-12  3:22   ` Masahiro Yamada
2019-10-10 15:14 ` [PATCH 3/4] symbol namespaces: revert to previous __ksymtab name scheme Matthias Maennich
2019-10-11 14:24   ` Will Deacon
2019-10-11 15:33   ` Greg Kroah-Hartman
2019-10-12  3:35   ` Masahiro Yamada
2019-10-10 15:14 ` [PATCH 4/4] export: avoid code duplication in include/linux/export.h Matthias Maennich
2019-10-11 15:31   ` Greg Kroah-Hartman
2019-10-11 15:43     ` Matthias Maennich [this message]
2019-10-12  4:25       ` Masahiro Yamada
2019-10-18  9:31 ` [PATCH v2 0/4] export/modpost: avoid renaming __ksymtab entries for symbol namespaces Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 1/4] modpost: delegate updating namespaces to separate function Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 2/4] modpost: make updating the symbol namespace explicit Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 3/4] symbol namespaces: revert to previous __ksymtab name scheme Matthias Maennich
2019-10-18  9:31   ` [PATCH v2 4/4] export: avoid code duplication in include/linux/export.h Matthias Maennich

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