sched, block: Unify cache detection
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
diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 1366a89..467c8de 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -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 @@
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 @@
*/
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);
diff --git a/block/blk.h b/block/blk.h
index 7efd772..df5b59a 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -164,22 +164,6 @@
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:
*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 513f524..0e19595 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1052,6 +1052,8 @@
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 @@
struct sched_domain_attr *dattr_new)
{
}
+
+static inline bool cpus_share_cache(int this_cpu, int that_cpu)
+{
+ return true;
+}
+
#endif /* !CONFIG_SMP */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5255c9d..d7c4322 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1507,7 +1507,7 @@
}
#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 @@
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 @@
*
* 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);
