linux-kernel - Re: [PATCH 02/18] flag parameters: socket and socketpair

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Message-ID: <Pine.LNX.4.64.0805051928230.20837@alien.or.mcafeemobile.com>
Date:	Mon, 5 May 2008 19:30:48 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Ulrich Drepper <drepper@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org, mtk.manpages@...il.com,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 02/18] flag parameters: socket and socketpair

On Mon, 5 May 2008, Andrew Morton wrote:

> On Mon, 5 May 2008 19:13:14 -0700 (PDT) Davide Libenzi <davidel@...ilserver.org> wrote:
> 
> > On Mon, 5 May 2008, Andrew Morton wrote:
> > 
> > > On Sun, 4 May 2008 23:42:46 -0400 Ulrich Drepper <drepper@...hat.com> wrote:
> > > 
> > > > +static const struct flags_rmap sock_file_flags_remap[] = {
> > > > +	{ SOCK_CLOEXEC, O_CLOEXEC },
> > > > +};
> > > > +
> > > >  asmlinkage long sys_socket(int family, int type, int protocol)
> > > >  {
> > > >  	int retval;
> > > >  	struct socket *sock;
> > > > +	int fflags;
> > > > +
> > > > +	type = flags_remap(sock_file_flags_remap,
> > > > +			   ARRAY_SIZE(sock_file_flags_remap),
> > > > +			   type, &fflags);
> > > 
> > > oh, so that's what it does.
> > > 
> > > afaict we only ever remap one or two flags.  Would it not be more efficient
> > > to do that inline?  Something along the lines of:
> > > 
> > > 	type = flag_remap(type, &fflags, SOCK_whatever, O_whatever);
> > > 	type = flag_remap(type, &fflags, SOCK_whatever2, O_whatever2);
> > > 
> > > ?
> > 
> > I think it is better to keep it able to remap more than one flag, with a 
> > single call, that is table driven.
> > 
> 
> The table-driven approach is slower for one and probably two bits and it is
> somewhat less readable.  What do we gain in return for this?

I think we can spend a few hours countering each other Pros&Cons about 
performance, size, style, etc...
Not worth if you ask me. So if you like the other way better, ask Uli to 
fix it your way.



- Davide


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