Date: Tue, 24 Jun 2003 12:25:51 +0200
From: Pavel Machek <pavel@suse.cz>
To: torvalds@transmeta.com, kernel list <linux-kernel@vger.kernel.org>,
       Rusty trivial patch monkey Russell 
	<trivial@rustcorp.com.au>
Subject: Re: Provide example copy_in_user implementation
Message-ID: <20030624102551.GE159@elf.ucw.cz>
References: <20030624100610.GC159@elf.ucw.cz> <20030624111820.D6478@flint.arm.linux.org.uk>
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On ?t 24-06-03 11:18:20, Russell King wrote:
> On Tue, Jun 24, 2003 at 12:06:10PM +0200, Pavel Machek wrote:
> > This patch adds example copy_in_user implementation (copy_in_user is
> > needed for new ioctl32 implementation, all 64bit archs will need
> > it)... Please apply,
> 
> get_user / put_user on byte quantities may be faster than using
> copy_from_user/copy_to_user on byte quantities.  Yes, it may be
> a generic implementation, but there's no point in purposely making
> it inefficient.

Actually, it seems that most architectures do...

static inline unsigned long
__copy_from_user(void *to, const void __user *from, unsigned long n)
{
        if (__builtin_constant_p(n)) {
                unsigned long ret;

                switch (n) {
                case 1:


...so it should be exactly as fast. Ahha, not arm.

If I wanted to optimize it, first step would be to copy over something
else than bytes. I'm afraid I do not want to optimize it.
								Pavel

-- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]
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