In message <200206202341.g5KNfqU07377@localhost.localdomain> you write:
> The hotplug CPU patch introduces this to replace the loop over all active CPUs
> abstraction:
>
> for (i = 0; i < NR_CPUS; i++) {
> if (!cpu_online(i))
> continue;
Yeah, it's simple, and none of the current ones are really critical.
But I think we're better off with:
for (i = first_cpu(); i < NR_CPUS; i = next_cpu(i)) {
Which is simple enough not to need an iterator macro, and also has the
bonus of giving irq-balancing et al. an efficient, portable way of
looking for the "next" cpu.
Cheers!
Rusty.
-- Anyone who quotes me in their sig is an idiot. -- Rusty Russell.Name: CPU iterator patch Author: Rusty Russell Status: Trivial
D: This patch adds first_cpu() & next_cpu(cpu) for more efficient cpu D: iteration.
diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.24/include/asm-i386/smp.h working-2.5.24-cpu-iter/include/asm-i386/smp.h --- linux-2.5.24/include/asm-i386/smp.h Thu Jun 20 01:28:51 2002 +++ working-2.5.24-cpu-iter/include/asm-i386/smp.h Sat Jun 22 00:55:46 2002 @@ -107,6 +107,18 @@ return -1; } +/* x86 is always linear, ie. cpu_online(0) always true at the moment. */ +static inline unsigned int first_cpu(void) +{ + return 0; +} + +/* Return "next" online cpu. Returns NR_CPUS on end. */ +static inline unsigned int next_cpu(unsigned int cpu) +{ + return find_next_bit(&cpu_online_map, NR_CPUS, cpu+1); +} + static __inline int hard_smp_processor_id(void) { /* we don't want to mark this access volatile - bad code generation */ diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.24/include/asm-ia64/smp.h working-2.5.24-cpu-iter/include/asm-ia64/smp.h --- linux-2.5.24/include/asm-ia64/smp.h Thu Jun 20 01:28:51 2002 +++ working-2.5.24-cpu-iter/include/asm-ia64/smp.h Sat Jun 22 00:59:34 2002 @@ -45,6 +45,17 @@ extern unsigned long ap_wakeup_vector; +static inline unsigned int first_cpu(void) +{ + return __ffs(cpu_online_map); +} + +/* Return "next" online cpu. Returns NR_CPUS on end. */ +static inline unsigned int next_cpu(unsigned int cpu) +{ + return find_next_bit(&cpu_online_map, NR_CPUS, cpu+1); +} + #define cpu_online(cpu) (cpu_online_map & (1<<(cpu))) extern inline unsigned int num_online_cpus(void) { diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.24/include/asm-ppc/smp.h working-2.5.24-cpu-iter/include/asm-ppc/smp.h --- linux-2.5.24/include/asm-ppc/smp.h Thu Jun 20 01:28:51 2002 +++ working-2.5.24-cpu-iter/include/asm-ppc/smp.h Sat Jun 22 00:58:37 2002 @@ -47,6 +47,17 @@ #define smp_processor_id() (current_thread_info()->cpu) +static inline unsigned int first_cpu(void) +{ + return __ffs(cpu_online_map); +} + +/* Return "next" online cpu. Returns NR_CPUS on end. */ +static inline unsigned int next_cpu(unsigned int cpu) +{ + return find_next_bit(&cpu_online_map, NR_CPUS, cpu+1); +} + #define cpu_online(cpu) (cpu_online_map & (1<<(cpu))) extern inline unsigned int num_online_cpus(void) diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.5.24/include/asm-sparc64/smp.h working-2.5.24-cpu-iter/include/asm-sparc64/smp.h --- linux-2.5.24/include/asm-sparc64/smp.h Fri Jun 21 09:41:55 2002 +++ working-2.5.24-cpu-iter/include/asm-sparc64/smp.h Sat Jun 22 01:06:58 2002 @@ -77,6 +77,17 @@ return -1; } +static inline unsigned int first_cpu(void) +{ + return __ffs(cpu_online_map); +} + +/* Return "next" online cpu. Returns NR_CPUS on end. */ +static inline unsigned int next_cpu(unsigned int cpu) +{ + return find_next_bit(&cpu_online_map, NR_CPUS, cpu+1); +} + /* * General functions that each host system must provide. */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sun Jun 23 2002 - 22:00:25 EST