The for_each_cpu_mask loop is used quite often in the kernel. It makes use of two functions: first_cpu and next_cpu. This patch changes for_each_cpu_mask to use only the latter. Because next_cpu finds the next eligible cpu _after_ the given one, the iteration variable has to be initialized to -1 and next_cpu has to be called with this value before the first iteration. An x86_64 defconfig kernel (from sched/latest) is about 2500 bytes smaller with this patch applied: text data bss dec hex filename 6222517 917952 749932 7890401 7865e1 vmlinux.orig 6219922 917952 749932 7887806 785bbe vmlinux The same size reduction is seen for defconfig+MAXSMP text data bss dec hex filename 6241772 2563968 1492716 10298456 9d2458 vmlinux.orig 6239211 2563968 1492716 10295895 9d1a57 vmlinux Signed-off-by: Alexander van Heukelum <heukelum@xxxxxxxxxxx> --- On Mon, May 12, 2008, Andreas Schwab wrote: > > +#define for_each_cpu_mask(cpu, mask) \ > > + for ((cpu) = ~((typeof(cpu))0); \ > > There is no need for such a complicated expression, -1 will work for > every (arithmetic) type. Indeed, thanks. This version applies on top of sched/latest. This version reuses the already-existing api next_cpu instead of inventing a new one; initializing the iteration counter to -1 was suggested by Matthew Wilcox. Now with a -1 instead of an overly carefull ~((typeof(cpu))0). "-1" is properly sign- extended even if cpu is u64 in a 32-bit environment. Greetings, Alexander include/linux/cpumask.h | 16 ++++++++-------- 1 files changed, 8 insertions(+), 8 deletions(-) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 73434e5..c24a556 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -377,10 +377,10 @@ int __any_online_cpu(const cpumask_t *mask); #define first_cpu(src) __first_cpu(&(src)) #define next_cpu(n, src) __next_cpu((n), &(src)) #define any_online_cpu(mask) __any_online_cpu(&(mask)) -#define for_each_cpu_mask(cpu, mask) \ - for ((cpu) = first_cpu(mask); \ - (cpu) < NR_CPUS; \ - (cpu) = next_cpu((cpu), (mask))) +#define for_each_cpu_mask(cpu, mask) \ + for ((cpu) = -1; \ + (cpu) = next_cpu((cpu), (mask)), \ + (cpu) < NR_CPUS; ) #endif #if NR_CPUS <= 64 @@ -394,10 +394,10 @@ int __any_online_cpu(const cpumask_t *mask); int __next_cpu_nr(int n, const cpumask_t *srcp); #define next_cpu_nr(n, src) __next_cpu_nr((n), &(src)) #define cpus_weight_nr(cpumask) __cpus_weight(&(cpumask), nr_cpu_ids) -#define for_each_cpu_mask_nr(cpu, mask) \ - for ((cpu) = first_cpu(mask); \ - (cpu) < nr_cpu_ids; \ - (cpu) = next_cpu_nr((cpu), (mask))) +#define for_each_cpu_mask_nr(cpu, mask) \ + for ((cpu) = -1; \ + (cpu) = next_cpu_nr((cpu), (mask)), \ + (cpu) < nr_cpu_ids; ) #endif /* NR_CPUS > 64 */ -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
