linux-kernel - Re: [PATCH v4 13/13] riscv: Add qspinlock support

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Message-ID: <20240821-6befd27b90a9e9ff89f4a277@orel>
Date: Wed, 21 Aug 2024 14:18:01 +0200
From: Andrew Jones <ajones@...tanamicro.com>
To: Guo Ren <guoren@...nel.org>
Cc: Alexandre Ghiti <alex@...ti.fr>, 
	Alexandre Ghiti <alexghiti@...osinc.com>, Jonathan Corbet <corbet@....net>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Andrea Parri <parri.andrea@...il.com>, 
	Nathan Chancellor <nathan@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>, 
	Boqun Feng <boqun.feng@...il.com>, Arnd Bergmann <arnd@...db.de>, 
	Leonardo Bras <leobras@...hat.com>, linux-doc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH v4 13/13] riscv: Add qspinlock support

On Sat, Aug 17, 2024 at 01:08:34PM GMT, Guo Ren wrote:
...
> > So I have just checked the size of the jump table section:
> >
> > * defconfig:
> >
> > - ticket: 26928 bytes
> > - combo: 28320 bytes
> >
> > So that's a ~5% increase.
> >
> > * ubuntu config
> >
> > - ticket: 107840 bytes
> > - combo: 174752 bytes
> >
> > And that's a ~62% increase.
> The size of the jump table section has increased from 5% to 62%. I
> think some configuration triggers the jump table's debug code. If it's
> not a debugging configuration, that's a bug of the Ubuntu config.

And I just remembered we wanted to check with CONFIG_CC_OPTIMIZE_FOR_SIZE

Thanks,
drew

> 
> >
> > This is the ELF size difference between ticket and combo spinlocks:
> >
> > * ticket: 776915592 bytes
> > * combo: 786958968 bytes
> >
> > So that's an increase of ~1.3% on the ELF.
> >
> > And the .text section size:
> >
> > * ticket: 12290960 bytes
> > * combo: 12366644 bytes
> >
> > And that's a ~0.6% increase!
> >
> > Finally, I'd say the impact is very limited :)
> >
> > Thanks,
> >
> > Alex
> >
> >