From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Date: Thu, 23 Sep 2004 07:17:25 +0000 Subject: Re: page fault scalability patch V8: [4/7] universally available Message-Id: <41527885.8020402@myrealbox.com> List-Id: References: <20040920205752.GH4242@wotan.suse.de> <200409211841.25507.vda@port.imtp.ilyichevsk.odessa.ua> <20040921154542.GB12132@wotan.suse.de> In-Reply-To: <20040921154542.GB12132@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andi Kleen Cc: Christoph Lameter , akpm@osdl.org, "David S. Miller" , benh@kernel.crashing.org, wli@holomorphy.com, davem@redhat.com, raybry@sgi.com, ak@muc.de, manfred@colorfullife.com, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, vrajesh@umich.edu, hugh@veritas.com Andi Kleen wrote: > On Tue, Sep 21, 2004 at 06:41:25PM +0300, Denis Vlasenko wrote: > >>On Monday 20 September 2004 23:57, Andi Kleen wrote: >> >>>On Mon, Sep 20, 2004 at 01:49:20PM -0700, Christoph Lameter wrote: >>> >>>>On Mon, 20 Sep 2004, Denis Vlasenko wrote: >>>> >>>> >>>>>I think it shouldn't be this way. >>>>> >>>>>OTOH for !CONFIG_386 case it makes perfect sense to have it inlined. >>>> >>>>Would the following revised patch be acceptable? >>> >>>You would need an EXPORT_SYMBOL at least. But to be honest your >>>original patch was much simpler and nicer and cmpxchg is not called >>>that often that it really matters. I would just ignore Denis' >>>suggestion and stay with the old patch. >> >>A bit faster approach (for CONFIG_386 case) would be using > > > It's actually slower. Many x86 CPUs cannot predict indirect jumps > and those that do cannot predict them as well as a test and jump. Wouldn't alternative_input() choosing between a cmpxchg and a call be the way to go here? Or is the overhead too high in an inline function? (No patch included since I don't pretend to understand gcc's asm syntax at all.) --Andy