The patch titled
cpuacct: refactoring cpuusage_read / cpuusage_write
has been added to the -mm tree. Its filename is
cpuacct-refactoring-cpuusage_read-cpuusage_write.patch
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------------------------------------------------------
Subject: cpuacct: refactoring cpuusage_read / cpuusage_write
From: Ken Chen <kenchen@xxxxxxxxxx>
In the thread regarding to 'export percpu cpuacct cgroup stats'
http://lkml.org/lkml/2008/12/7/13
akpm pointed out that current cpuacct code is inefficient. This patch
refactoring the following:
* make cpu_rq locking only on 32-bit
* change iterator to each_present_cpu instead of each_possible_cpu to
make it hotplug friendly.
It's a bit of code churn, but I was rewarded with 160 byte code size saving
on x86-64 arch and zero code size change on i386.
Signed-off-by: Ken Chen <kenchen@xxxxxxxxxx>
Reviewed-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched.c | 56 ++++++++++++++++++++++++++++++++---------------
1 file changed, 39 insertions(+), 17 deletions(-)
diff -puN kernel/sched.c~cpuacct-refactoring-cpuusage_read-cpuusage_write kernel/sched.c
--- a/kernel/sched.c~cpuacct-refactoring-cpuusage_read-cpuusage_write
+++ a/kernel/sched.c
@@ -9391,6 +9391,41 @@ cpuacct_destroy(struct cgroup_subsys *ss
kfree(ca);
}
+static u64 cpuacct_cpuusage_read(struct cpuacct *ca, int cpu)
+{
+ u64 *cpuusage = percpu_ptr(ca->cpuusage, cpu);
+ u64 data;
+
+#ifndef CONFIG_64BIT
+ /*
+ * Take rq->lock to make 64-bit read safe on 32-bit platforms.
+ */
+ spin_lock_irq(&cpu_rq(cpu)->lock);
+ data = *cpuusage;
+ spin_unlock_irq(&cpu_rq(cpu)->lock);
+#else
+ data = *cpuusage;
+#endif
+
+ return data;
+}
+
+static void cpuacct_cpuusage_write(struct cpuacct *ca, int cpu, u64 val)
+{
+ u64 *cpuusage = percpu_ptr(ca->cpuusage, cpu);
+
+#ifndef CONFIG_64BIT
+ /*
+ * Take rq->lock to make 64-bit write safe on 32-bit platforms.
+ */
+ spin_lock_irq(&cpu_rq(cpu)->lock);
+ *cpuusage = val;
+ spin_unlock_irq(&cpu_rq(cpu)->lock);
+#else
+ *cpuusage = val;
+#endif
+}
+
/* return total cpu usage (in nanoseconds) of a group */
static u64 cpuusage_read(struct cgroup *cgrp, struct cftype *cft)
{
@@ -9398,17 +9433,8 @@ static u64 cpuusage_read(struct cgroup *
u64 totalcpuusage = 0;
int i;
- for_each_possible_cpu(i) {
- u64 *cpuusage = percpu_ptr(ca->cpuusage, i);
-
- /*
- * Take rq->lock to make 64-bit addition safe on 32-bit
- * platforms.
- */
- spin_lock_irq(&cpu_rq(i)->lock);
- totalcpuusage += *cpuusage;
- spin_unlock_irq(&cpu_rq(i)->lock);
- }
+ for_each_present_cpu(i)
+ totalcpuusage += cpuacct_cpuusage_read(ca, i);
return totalcpuusage;
}
@@ -9425,13 +9451,9 @@ static int cpuusage_write(struct cgroup
goto out;
}
- for_each_possible_cpu(i) {
- u64 *cpuusage = percpu_ptr(ca->cpuusage, i);
+ for_each_present_cpu(i)
+ cpuacct_cpuusage_write(ca, i, 0);
- spin_lock_irq(&cpu_rq(i)->lock);
- *cpuusage = 0;
- spin_unlock_irq(&cpu_rq(i)->lock);
- }
out:
return err;
}
_
Patches currently in -mm which might be from kenchen@xxxxxxxxxx are
linux-next.patch
cpuacct-refactoring-cpuusage_read-cpuusage_write.patch
cpuacct-export-percpu-cpuacct-cgroup-stats.patch
hugetlb-unsigned-ret-cannot-be-negative.patch
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