diff options
author | Ken Chen <kenchen@google.com> | 2008-12-16 09:02:01 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-12-16 14:15:00 +0300 |
commit | 720f54988e17b33f3f477010b3a68ee872d20d5a (patch) | |
tree | ebb475d1a7af97926c1f469a57bef47c46e9ae98 /kernel | |
parent | 34f28ecd0f4bdc733c681294d02d9fab5880591b (diff) | |
download | linux-720f54988e17b33f3f477010b3a68ee872d20d5a.tar.xz |
sched, cpuacct: refactoring cpuusage_read / cpuusage_write
Impact: micro-optimize the code on 64-bit architectures
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@google.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched.c | 56 |
1 files changed, 39 insertions, 17 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 88215066efae..41b7e2d524d6 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -9275,6 +9275,41 @@ cpuacct_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp) 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) { @@ -9282,17 +9317,8 @@ static u64 cpuusage_read(struct cgroup *cgrp, struct cftype *cft) 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; } @@ -9309,13 +9335,9 @@ static int cpuusage_write(struct cgroup *cgrp, struct cftype *cftype, 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; } |