linux-kernel - Re: [PATCH 00/13] [PATCH RFC] Paravirtualized ticketlocks

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Date:	Fri, 2 Sep 2011 13:27:44 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...nel.dk>, Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	KVM <kvm@...r.kernel.org>, Andi Kleen <andi@...stfloor.org>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: [PATCH 00/13] [PATCH RFC] Paravirtualized ticketlocks

On Fri, Sep 2, 2011 at 1:07 PM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
> I don't know whether that fastpath code is small enough to consider
> inlining everywhere?

No.

There's no point in inlining something that ends up containing a
conditional function call: gcc will have to effectively save/restore
registers around that thing anyway, so you lose a lot of the
advantages of inlining. So I think it's better done as an out-of-line
function, which I thought we did for spinlocks anyway.

Also, do you run with CONFIG_OPTIMIZE_SIZE? Without that, gcc should
be smart enough to make a "likely()" case be a fall-through.

                          Linus
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