| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20131022221138.GJ2490@laptop.programming.kicks-ass.net>
Date: Wed, 23 Oct 2013 00:11:38 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc: Mike Galbraith <bitbucket@...ine.de>, Paul Turner <pjt@...gle.com>,
Ingo Molnar <mingo@...nel.org>,
Michael Neuling <mikey@...ling.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linux-kernel@...r.kernel.org, Anton Blanchard <anton@...ba.org>,
Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/3] sched: Fix nohz_kick_needed to consider the nr_busy
of the parent domain's group
On Mon, Oct 21, 2013 at 05:14:42PM +0530, Vaidyanathan Srinivasan wrote:
> kernel/sched/fair.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 7c70201..12f0eab 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5807,12 +5807,19 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu)
>
> rcu_read_lock();
> for_each_domain(cpu, sd) {
> + struct sched_domain *sd_parent = sd->parent;
> + struct sched_group *sg;
> + struct sched_group_power *sgp;
> + int nr_busy;
> +
> + if (sd_parent) {
> + sg = sd_parent->groups;
> + sgp = sg->sgp;
> + nr_busy = atomic_read(&sgp->nr_busy_cpus);
> +
> + if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
> + goto need_kick_unlock;
> + }
>
> if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
> && (cpumask_first_and(nohz.idle_cpus_mask,
>
Almost I'd say; what happens on !sd_parent && SD_ASYM_PACKING ?
Also, this made me look at the nr_busy stuff again, and somehow that
entire thing makes me a little sad.
Can't we do something like the below and cut that nr_busy sd iteration
short?
This nohz stuff really needs to be re-thought and made more scalable --
its a royal pain :/
kernel/sched/core.c | 4 ++++
kernel/sched/fair.c | 21 +++++++++++++++------
kernel/sched/sched.h | 5 ++---
3 files changed, 21 insertions(+), 9 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c06b8d3..89db8dc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5271,6 +5271,7 @@ DEFINE_PER_CPU(struct sched_domain *, sd_llc);
DEFINE_PER_CPU(int, sd_llc_size);
DEFINE_PER_CPU(int, sd_llc_id);
DEFINE_PER_CPU(struct sched_domain *, sd_numa);
+DEFINE_PER_CPU(struct sched_domain *, sd_busy);
static void update_top_cache_domain(int cpu)
{
@@ -5290,6 +5291,9 @@ static void update_top_cache_domain(int cpu)
sd = lowest_flag_domain(cpu, SD_NUMA);
rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
+
+ sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING);
+ rcu_assign_pointer(per_cpu(sd_busy, cpu), sd);
}
/*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 813dd61..3d5141e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6512,19 +6512,23 @@ static inline void nohz_balance_exit_idle(int cpu)
}
}
-static inline void set_cpu_sd_state_busy(void)
+static inline void set_cpu_sd_state_busy(int cpu)
{
struct sched_domain *sd;
+ struct rq *rq = cpu_rq(cpu);
rcu_read_lock();
- sd = rcu_dereference_check_sched_domain(this_rq()->sd);
+ sd = rcu_dereference_check_sched_domain(rq->sd);
if (!sd || !sd->nohz_idle)
goto unlock;
sd->nohz_idle = 0;
- for (; sd; sd = sd->parent)
+ for (; sd; sd = sd->parent) {
atomic_inc(&sd->groups->sgp->nr_busy_cpus);
+ if (sd == per_cpu(sd_busy, cpu))
+ break;
+ }
unlock:
rcu_read_unlock();
}
@@ -6532,16 +6536,21 @@ static inline void set_cpu_sd_state_busy(void)
void set_cpu_sd_state_idle(void)
{
struct sched_domain *sd;
+ int cpu = smp_processor_id();
+ struct rq *rq = cpu_rq(cpu);
rcu_read_lock();
- sd = rcu_dereference_check_sched_domain(this_rq()->sd);
+ sd = rcu_dereference_check_sched_domain(rq->sd);
if (!sd || sd->nohz_idle)
goto unlock;
sd->nohz_idle = 1;
- for (; sd; sd = sd->parent)
+ for (; sd; sd = sd->parent) {
atomic_dec(&sd->groups->sgp->nr_busy_cpus);
+ if (sd == per_cpu(sd_busy, cpu))
+ break;
+ }
unlock:
rcu_read_unlock();
}
@@ -6756,7 +6765,7 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu)
* We may be recently in ticked or tickless idle mode. At the first
* busy tick after returning from idle, we will update the busy stats.
*/
- set_cpu_sd_state_busy();
+ set_cpu_sd_state_busy(cpu);
nohz_balance_exit_idle(cpu);
/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ffc7087..80c5fd2 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -599,9 +599,8 @@ static inline struct sched_domain *highest_flag_domain(int cpu, int flag)
struct sched_domain *sd, *hsd = NULL;
for_each_domain(cpu, sd) {
- if (!(sd->flags & flag))
- break;
- hsd = sd;
+ if (sd->flags & flag)
+ hsd = sd;
}
return hsd;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists