* Rusty Russell ([EMAIL PROTECTED]) wrote: > On Saturday 17 November 2007 01:03:35 Mathieu Desnoyers wrote: > > x86 optimization of the immediate values which uses a movl with code > > patching to set/unset the value used to populate the register used as > > variable source. > > Since immediate values are by definition an optimization, I think it makes > sense to insist they be 1, 2, 4 or 8 bytes. A BUILD_BUG_ON() in the right > place should ensure this (probably in generic code rather than x86). > sure,
> > =================================================================== > > --- linux-2.6-lttng.orig/arch/x86/kernel/traps_32.c > > I don't think you need any modification to this file now. > yep, > > + * Create the instruction in a discarded section to calculate its size. > > This is > > + * how we can align the beginning of the instruction on an address that > > will > > + * permit atomic modificatino of the immediate value without knowing the > > size of > > + * the opcode used by the compiler. The operand size is known in advance. > > + */ > > This alignment is also now unnecessary. > right, > > +++ linux-2.6-lttng/arch/x86/kernel/immediate.c 2007-11-16 > > 08:56:22.000000000 -0500 @@ -0,0 +1,143 @@ > > +/* > > + * Immediate Value - x86 architecture specific code. > > This is now almost entirely generic code, but I suppose we can let the next > architecture hoist it out. > I'll move it to kernel/immediate.c. We can therefore remove the powerpc immediate.c as well. > > +/** > > + * arch_immediate_update_early - update one immediate value at boot time > > + * @immediate: pointer of type const struct __immediate to update > > + * > > + * Update one immediate value at boot time. > > + */ > > +void arch_immediate_update_early(const struct __immediate *immediate) > > I think it would be easier to just fast-path the num_online_cpus == 1 case, > even if you want to keep this "update_early" interface. > Nope, that could lead to problems. I call core_immediate_update() _very_ early, before boot_cpu_init() is called. Therefore, cpu_online_map is not set yet. I am not sure the benefit of using num_online_cpus outweights the added fragility wrt other boot process initializations. > But I like your IPI algorithm: very tight. > Thanks. Many thanks for the review, I'll repost the patchset for comments. Mathieu -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
