Messages in this thread |  | | | Date | Thu, 23 Sep 2004 00:17:25 -0700 | | From | Andy Lutomirski <> | | Subject | Re: page fault scalability patch V8: [4/7] universally available cmpxchg on i386 |
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.)
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