From: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Paolo Abeni <pabeni@redhat.com>,
"x86@kernel.org" <x86@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Hannes Frederic Sowa <hannes@stressinduktion.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/uaccess: use unrolled string copy for short strings
Date: Thu, 22 Jun 2017 15:55:49 +0100 [thread overview]
Message-ID: <20170622155549.57dfc856@alans-desktop> (raw)
In-Reply-To: <CAGXu5j+1yjqgbfYT-JVQC=MstJxUNzqhr3E4WGKS+82rSHaaVA@mail.gmail.com>
> > diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
> > index c5504b9..16a8871 100644
> > --- a/arch/x86/include/asm/uaccess_64.h
> > +++ b/arch/x86/include/asm/uaccess_64.h
> > @@ -28,6 +28,9 @@ copy_user_generic(void *to, const void *from, unsigned len)
> > {
> > unsigned ret;
> >
> > + if (len <= 64)
> > + return copy_user_generic_unrolled(to, from, len);
> > +
Given this gets inlined surely that should bracketed with an ifdef
against optimizing for space.
Also you give one set of benchmarks but how do they look on different
processors - AMD v Intel, Atom v Core, Ryzen v older AMD etc ?
Alan
next prev parent reply other threads:[~2017-06-22 14:56 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-21 11:09 [PATCH] x86/uaccess: use unrolled string copy for short strings Paolo Abeni
2017-06-21 17:38 ` Kees Cook
2017-06-22 14:55 ` Alan Cox [this message]
2017-06-22 8:47 ` Ingo Molnar
2017-06-22 17:02 ` Paolo Abeni
2017-06-22 17:30 ` Linus Torvalds
2017-06-22 17:54 ` Paolo Abeni
2017-06-29 13:55 ` [PATCH] x86/uaccess: optimize copy_user_enhanced_fast_string for short string Paolo Abeni
2017-06-29 21:40 ` Linus Torvalds
2017-06-30 13:10 ` [tip:x86/asm] x86/uaccess: Optimize copy_user_enhanced_fast_string() for short strings tip-bot for Paolo Abeni
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