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From: Christophe LEROY <christophe.leroy@c-s.fr>
To: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: usercopy in PPC64
Date: Wed, 31 May 2017 08:55:30 +0200	[thread overview]
Message-ID: <21ab485d-84f9-6803-a2b9-65d3a5928e59@c-s.fr> (raw)
In-Reply-To: <d25be832-2030-4bc8-dbc5-4baebb759279@c-s.fr>


Le 30/05/2017 à 14:36, Christophe LEROY a écrit :
> Hi all powerpc64 experts,
> 
> While looking at the usercopy efficiency for PPC32, I noticed something 
> which looks strange.
> 
> In asm/uaccess.h, raw_copy_from_user() and raw_copy_to_user() implements 
> a fast path using get_user() and put_user() for copies of constant size 
> < 8.
> 
> But INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER are only defined for 
> PPC32, so PPC64 will call __copy_tofrom_user() even for small constant 
> size copies. Is that wanted ?
> 

I tried and built ppc64_defconfig with and without INLINE_COPY_xxx_USER, 
I got the following result:

Without INLINE_COPY_xxx_USER:
System.map:c0000000009b2000 A _etext

With INLINE_COPY_xxx_USER:
System.map:c0000000009c1000 A _etext

So the size increase with inlining is only 0,6%
Wouldn't it be worth it ?

Christophe

      reply	other threads:[~2017-05-31  6:55 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-30 12:36 usercopy in PPC64 Christophe LEROY
2017-05-31  6:55 ` Christophe LEROY [this message]

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