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SubjectRe: [PATCH] lib/cpumask.c: Optimize __any_online_cpu() calculation
On 02/15/2012 06:27 PM, Eric Dumazet wrote:

> Le mercredi 15 février 2012 à 18:05 +0530, Srivatsa S. Bhat a écrit :
>> __any_online_cpu() uses a for loop at the moment.
>> Instead, use cpumask_* operations to speed it up.
>>
>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>> ---
>> Actually, the patch posted at https://lkml.org/lkml/2012/2/15/101 removed
>> the last user of any_online_cpu() (and hence __any_online_cpu()).
>> However, since this is an exported symbol, I refrained from removing this
>> function altogether.
>
> Just remove the export/function and eventually leave the helper ?
>
> #define any_online_cpu(mask) cpumask_any_and(mask, cpu_online_mask)
>


That sounds good. Here is v2 of the patch.
(Since this v2 touches include/linux/cpumask.h, I rebased it on top of the
patch posted at: https://lkml.org/lkml/2012/2/15/2. Even without that
patch it should apply with minor line number changes..)

---
From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Subject: [PATCH v2] lib/cpumask.c: Remove __any_online_cpu()
__any_online_cpu() is not optimal and also unnecessary.
So, replace its use by faster cpumask_* operations.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
include/linux/cpumask.h | 3 +--
lib/cpumask.c | 12 ------------
2 files changed, 1 insertions(+), 14 deletions(-)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 42fec19..d3ccd2d 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -808,11 +808,10 @@ static inline const struct cpumask *get_cpu_mask(unsigned int cpu)
#else /* NR_CPUS > 1 */
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 any_online_cpu(mask) cpumask_any_and(&mask, cpu_online_mask)
#define for_each_cpu_mask(cpu, mask) \
for ((cpu) = -1; \
(cpu) = next_cpu((cpu), (mask)), \
diff --git a/lib/cpumask.c b/lib/cpumask.c
index af3e5817..0470742 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -26,18 +26,6 @@ int __next_cpu_nr(int n, const cpumask_t *srcp)
EXPORT_SYMBOL(__next_cpu_nr);
#endif

-int __any_online_cpu(const cpumask_t *mask)
-{
- int cpu;
-
- for_each_cpu(cpu, mask) {
- if (cpu_online(cpu))
- break;
- }
- return cpu;
-}
-EXPORT_SYMBOL(__any_online_cpu);
-
/**
* cpumask_next_and - get the next cpu in *src1p & *src2p
* @n: the cpu prior to the place to search (ie. return will be > @n)

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