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sched, block: Unify cache detection

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The block layer has some code trying to determine if two CPUs share a
cache, the scheduler has a similar function. Expose the function used
by the scheduler and make the block layer use it, thereby removing the
block layers usage of CONFIG_SCHED* and topology bits.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Jens Axboe <axboe@kernel.dk>
Link: http://lkml.kernel.org/r/1327579450.2446.95.camel@twins
This commit is contained in:
Peter Zijlstra 2012-01-26 12:44:34 +01:00 committed by Ingo Molnar
parent cb297a3e43
commit 39be350127
4 changed files with 19 additions and 27 deletions
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16
block/blk-softirq.c
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@ -8,6 +8,7 @@
#include <linux/blkdev.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/sched.h>
#include "blk.h"
@ -103,9 +104,10 @@ static struct notifier_block __cpuinitdata blk_cpu_notifier = {
void __blk_complete_request(struct request *req)
{
int ccpu, cpu, group_cpu = NR_CPUS;
int ccpu, cpu;
struct request_queue *q = req->q;
unsigned long flags;
bool shared = false;
BUG_ON(!q->softirq_done_fn);
@ -117,22 +119,20 @@ void __blk_complete_request(struct request *req)
*/
if (req->cpu != -1) {
ccpu = req->cpu;
if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) {
ccpu = blk_cpu_to_group(ccpu);
group_cpu = blk_cpu_to_group(cpu);
}
if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
shared = cpus_share_cache(cpu, ccpu);
} else
ccpu = cpu;
/*
* If current CPU and requested CPU are in the same group, running
* softirq in current CPU. One might concern this is just like
* If current CPU and requested CPU share a cache, run the softirq on
* the current CPU. One might concern this is just like
* QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
* running in interrupt handler, and currently I/O controller doesn't
* support multiple interrupts, so current CPU is unique actually. This
* avoids IPI sending from current CPU to the first CPU of a group.
*/
if (ccpu == cpu || ccpu == group_cpu) {
if (ccpu == cpu || shared) {
struct list_head *list;
do_local:
list = &__get_cpu_var(blk_cpu_done);

16
block/blk.h
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@ -164,22 +164,6 @@ static inline int queue_congestion_off_threshold(struct request_queue *q)
return q->nr_congestion_off;
}
static inline int blk_cpu_to_group(int cpu)
{
int group = NR_CPUS;
#ifdef CONFIG_SCHED_MC
const struct cpumask *mask = cpu_coregroup_mask(cpu);
group = cpumask_first(mask);
#elif defined(CONFIG_SCHED_SMT)
group = cpumask_first(topology_thread_cpumask(cpu));
#else
return cpu;
#endif
if (likely(group < NR_CPUS))
return group;
return cpu;
}
/*
* Contribute to IO statistics IFF:
*

8
include/linux/sched.h
View File

@ -1052,6 +1052,8 @@ static inline int test_sd_parent(struct sched_domain *sd, int flag)
unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu);
unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu);
bool cpus_share_cache(int this_cpu, int that_cpu);
#else /* CONFIG_SMP */
struct sched_domain_attr;
@ -1061,6 +1063,12 @@ partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
struct sched_domain_attr *dattr_new)
{
}
static inline bool cpus_share_cache(int this_cpu, int that_cpu)
{
return true;
}
#endif /* !CONFIG_SMP */

6
kernel/sched/core.c
View File

@ -1507,7 +1507,7 @@ static int ttwu_activate_remote(struct task_struct *p, int wake_flags)
}
#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
static inline int ttwu_share_cache(int this_cpu, int that_cpu)
bool cpus_share_cache(int this_cpu, int that_cpu)
{
return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
}
@ -1518,7 +1518,7 @@ static void ttwu_queue(struct task_struct *p, int cpu)
struct rq *rq = cpu_rq(cpu);
#if defined(CONFIG_SMP)
if (sched_feat(TTWU_QUEUE) && !ttwu_share_cache(smp_processor_id(), cpu)) {
if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
sched_clock_cpu(cpu); /* sync clocks x-cpu */
ttwu_queue_remote(p, cpu);
return;
@ -5754,7 +5754,7 @@ static void destroy_sched_domains(struct sched_domain *sd, int cpu)
*
* Also keep a unique ID per domain (we use the first cpu number in
* the cpumask of the domain), this allows us to quickly tell if
* two cpus are in the same cache domain, see ttwu_share_cache().
* two cpus are in the same cache domain, see cpus_share_cache().
*/
DEFINE_PER_CPU(struct sched_domain *, sd_llc);
DEFINE_PER_CPU(int, sd_llc_id);