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x86: Add performance variants of cpumask operators 

* Increase performance for systems with large count NR_CPUS by limiting
    the range of the cpumask operators that loop over the bits in a cpumask_t
    variable.  This removes a large amount of wasted cpu cycles.

  * Add performance variants of the cpumask operators:

    int cpus_weight_nr(mask)	     Same using nr_cpu_ids instead of NR_CPUS
    int first_cpu_nr(mask)	     Number lowest set bit, or nr_cpu_ids
    int next_cpu_nr(cpu, mask)	     Next cpu past 'cpu', or nr_cpu_ids
    for_each_cpu_mask_nr(cpu, mask)  for-loop cpu over mask using nr_cpu_ids

  * Modify following to use performance variants:

    #define num_online_cpus()	cpus_weight_nr(cpu_online_map)
    #define num_possible_cpus()	cpus_weight_nr(cpu_possible_map)
    #define num_present_cpus()	cpus_weight_nr(cpu_present_map)

    #define for_each_possible_cpu(cpu) for_each_cpu_mask_nr((cpu), ...)
    #define for_each_online_cpu(cpu)   for_each_cpu_mask_nr((cpu), ...)
    #define for_each_present_cpu(cpu)  for_each_cpu_mask_nr((cpu), ...)

  * Comment added to include/linux/cpumask.h:

    Note: The alternate operations with the suffix "_nr" are used
	  to limit the range of the loop to nr_cpu_ids instead of
	  NR_CPUS when NR_CPUS > 64 for performance reasons.
	  If NR_CPUS is <= 64 then most assembler bitmask
	  operators execute faster with a constant range, so
	  the operator will continue to use NR_CPUS.

	  Another consideration is that nr_cpu_ids is initialized
	  to NR_CPUS and isn't lowered until the possible cpus are
	  discovered (including any disabled cpus).  So early uses
	  will span the entire range of NR_CPUS.

    (The net effect is that for systems with 64 or less CPU's there are no
     functional changes.)

For inclusion into sched-devel/latest tree.

Based on:
	git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
    +   sched-devel/latest  .../mingo/linux-2.6-sched-devel.git

Cc: Paul Jackson <pj@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Reviewed-by: Paul Jackson <pj@sgi.com>
Reviewed-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Travis 2008-05-12 21:21:13 +02:00 committed by Thomas Gleixner
parent 143aa5c53b
commit 41df0d61c2
2 changed files with 71 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

92
include/linux/cpumask.h
View File

@ -17,6 +17,20 @@
* For details of cpus_onto(), see bitmap_onto in lib/bitmap.c.
* For details of cpus_fold(), see bitmap_fold in lib/bitmap.c.
*
* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
* Note: The alternate operations with the suffix "_nr" are used
* to limit the range of the loop to nr_cpu_ids instead of
* NR_CPUS when NR_CPUS > 64 for performance reasons.
* If NR_CPUS is <= 64 then most assembler bitmask
* operators execute faster with a constant range, so
* the operator will continue to use NR_CPUS.
*
* Another consideration is that nr_cpu_ids is initialized
* to NR_CPUS and isn't lowered until the possible cpus are
* discovered (including any disabled cpus). So early uses
* will span the entire range of NR_CPUS.
* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
*
* The available cpumask operations are:
*
* void cpu_set(cpu, mask) turn on bit 'cpu' in mask
@ -38,12 +52,14 @@
* int cpus_empty(mask) Is mask empty (no bits sets)?
* int cpus_full(mask) Is mask full (all bits sets)?
* int cpus_weight(mask) Hamming weigh - number of set bits
* int cpus_weight_nr(mask) Same using nr_cpu_ids instead of NR_CPUS
*
* void cpus_shift_right(dst, src, n) Shift right
* void cpus_shift_left(dst, src, n) Shift left
*
* int first_cpu(mask) Number lowest set bit, or NR_CPUS
* int next_cpu(cpu, mask) Next cpu past 'cpu', or NR_CPUS
* int next_cpu_nr(cpu, mask) Next cpu past 'cpu', or nr_cpu_ids
*
* cpumask_t cpumask_of_cpu(cpu) Return cpumask with bit 'cpu' set
* CPU_MASK_ALL Initializer - all bits set
@ -59,7 +75,8 @@
* void cpus_onto(dst, orig, relmap) *dst = orig relative to relmap
* void cpus_fold(dst, orig, sz) dst bits = orig bits mod sz
*
* for_each_cpu_mask(cpu, mask) for-loop cpu over mask
* for_each_cpu_mask(cpu, mask) for-loop cpu over mask using NR_CPUS
* for_each_cpu_mask_nr(cpu, mask) for-loop cpu over mask using nr_cpu_ids
*
* int num_online_cpus() Number of online CPUs
* int num_possible_cpus() Number of all possible CPUs
@ -216,15 +233,6 @@ static inline void __cpus_shift_left(cpumask_t *dstp,
bitmap_shift_left(dstp->bits, srcp->bits, n, nbits);
}
#ifdef CONFIG_SMP
int __first_cpu(const cpumask_t *srcp);
#define first_cpu(src) __first_cpu(&(src))
int __next_cpu(int n, const cpumask_t *srcp);
#define next_cpu(n, src) __next_cpu((n), &(src))
#else
#define first_cpu(src) ({ (void)(src); 0; })
#define next_cpu(n, src) ({ (void)(src); 1; })
#endif
#ifdef CONFIG_HAVE_CPUMASK_OF_CPU_MAP
extern cpumask_t *cpumask_of_cpu_map;
@ -343,15 +351,48 @@ static inline void __cpus_fold(cpumask_t *dstp, const cpumask_t *origp,
bitmap_fold(dstp->bits, origp->bits, sz, nbits);
}
#if NR_CPUS > 1
#if NR_CPUS == 1
#define nr_cpu_ids 1
#define first_cpu(src) ({ (void)(src); 0; })
#define next_cpu(n, src) ({ (void)(src); 1; })
#define any_online_cpu(mask) 0
#define for_each_cpu_mask(cpu, mask) \
for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
#else /* NR_CPUS > 1 */
extern int nr_cpu_ids;
int __first_cpu(const cpumask_t *srcp);
int __next_cpu(int n, const cpumask_t *srcp);
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)))
#else /* NR_CPUS == 1 */
#define for_each_cpu_mask(cpu, mask) \
for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
#endif /* NR_CPUS */
#endif
#if NR_CPUS <= 64
#define next_cpu_nr(n, src) next_cpu(n, src)
#define cpus_weight_nr(cpumask) cpus_weight(cpumask)
#define for_each_cpu_mask_nr(cpu, mask) for_each_cpu_mask(cpu, mask)
#else /* NR_CPUS > 64 */
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)))
#endif /* NR_CPUS > 64 */
/*
* The following particular system cpumasks and operations manage
@ -414,9 +455,9 @@ extern cpumask_t cpu_online_map;
extern cpumask_t cpu_present_map;
#if NR_CPUS > 1
#define num_online_cpus() cpus_weight(cpu_online_map)
#define num_possible_cpus() cpus_weight(cpu_possible_map)
#define num_present_cpus() cpus_weight(cpu_present_map)
#define num_online_cpus() cpus_weight_nr(cpu_online_map)
#define num_possible_cpus() cpus_weight_nr(cpu_possible_map)
#define num_present_cpus() cpus_weight_nr(cpu_present_map)
#define cpu_online(cpu) cpu_isset((cpu), cpu_online_map)
#define cpu_possible(cpu) cpu_isset((cpu), cpu_possible_map)
#define cpu_present(cpu) cpu_isset((cpu), cpu_present_map)
@ -431,17 +472,8 @@ extern cpumask_t cpu_present_map;
#define cpu_is_offline(cpu) unlikely(!cpu_online(cpu))
#ifdef CONFIG_SMP
extern int nr_cpu_ids;
#define any_online_cpu(mask) __any_online_cpu(&(mask))
int __any_online_cpu(const cpumask_t *mask);
#else
#define nr_cpu_ids 1
#define any_online_cpu(mask) 0
#endif
#define for_each_possible_cpu(cpu) for_each_cpu_mask((cpu), cpu_possible_map)
#define for_each_online_cpu(cpu) for_each_cpu_mask((cpu), cpu_online_map)
#define for_each_present_cpu(cpu) for_each_cpu_mask((cpu), cpu_present_map)
#define for_each_possible_cpu(cpu) for_each_cpu_mask_nr((cpu), cpu_possible_map)
#define for_each_online_cpu(cpu) for_each_cpu_mask_nr((cpu), cpu_online_map)
#define for_each_present_cpu(cpu) for_each_cpu_mask_nr((cpu), cpu_present_map)
#endif /* __LINUX_CPUMASK_H */

9
lib/cpumask.c
View File

@ -15,6 +15,15 @@ int __next_cpu(int n, const cpumask_t *srcp)
}
EXPORT_SYMBOL(__next_cpu);
#if NR_CPUS > 64
int __next_cpu_nr(int n, const cpumask_t *srcp)
{
return min_t(int, nr_cpu_ids,
find_next_bit(srcp->bits, nr_cpu_ids, n+1));
}
EXPORT_SYMBOL(__next_cpu_nr);
#endif
int __any_online_cpu(const cpumask_t *mask)
{
int cpu;