From 08c183f31bdbb709f177f6d3110d5f288ea33933 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Sun, 10 Dec 2006 02:20:29 -0800 Subject: [PATCH] [PATCH] sched: add option to serialize load balancing Large sched domains can be very expensive to scan. Add an option SD_SERIALIZE to the sched domain flags. If that flag is set then we make sure that no other such domain is being balanced. [akpm@osdl.org: build fix] Signed-off-by: Christoph Lameter Cc: Peter Williams Cc: Nick Piggin Cc: Christoph Lameter Cc: "Siddha, Suresh B" Cc: "Chen, Kenneth W" Acked-by: Ingo Molnar Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-i386/topology.h | 1 + include/asm-ia64/topology.h | 1 + include/asm-powerpc/topology.h | 1 + include/asm-x86_64/topology.h | 1 + include/linux/sched.h | 1 + include/linux/topology.h | 3 ++- kernel/sched.c | 9 +++++++++ 7 files changed, 16 insertions(+), 1 deletion(-) diff --git a/include/asm-i386/topology.h b/include/asm-i386/topology.h index 978d0959613..ac58580ad66 100644 --- a/include/asm-i386/topology.h +++ b/include/asm-i386/topology.h @@ -89,6 +89,7 @@ static inline int node_to_first_cpu(int node) .flags = SD_LOAD_BALANCE \ | SD_BALANCE_EXEC \ | SD_BALANCE_FORK \ + | SD_SERIALIZE \ | SD_WAKE_BALANCE, \ .last_balance = jiffies, \ .balance_interval = 1, \ diff --git a/include/asm-ia64/topology.h b/include/asm-ia64/topology.h index a6e38565ab4..22ed6749557 100644 --- a/include/asm-ia64/topology.h +++ b/include/asm-ia64/topology.h @@ -101,6 +101,7 @@ void build_cpu_to_node_map(void); .flags = SD_LOAD_BALANCE \ | SD_BALANCE_EXEC \ | SD_BALANCE_FORK \ + | SD_SERIALIZE \ | SD_WAKE_BALANCE, \ .last_balance = jiffies, \ .balance_interval = 64, \ diff --git a/include/asm-powerpc/topology.h b/include/asm-powerpc/topology.h index 50c014007de..6610495f5f1 100644 --- a/include/asm-powerpc/topology.h +++ b/include/asm-powerpc/topology.h @@ -66,6 +66,7 @@ static inline int pcibus_to_node(struct pci_bus *bus) | SD_BALANCE_EXEC \ | SD_BALANCE_NEWIDLE \ | SD_WAKE_IDLE \ + | SD_SERIALIZE \ | SD_WAKE_BALANCE, \ .last_balance = jiffies, \ .balance_interval = 1, \ diff --git a/include/asm-x86_64/topology.h b/include/asm-x86_64/topology.h index 5c8f49280db..2facec5914d 100644 --- a/include/asm-x86_64/topology.h +++ b/include/asm-x86_64/topology.h @@ -47,6 +47,7 @@ extern int __node_distance(int, int); .flags = SD_LOAD_BALANCE \ | SD_BALANCE_FORK \ | SD_BALANCE_EXEC \ + | SD_SERIALIZE \ | SD_WAKE_BALANCE, \ .last_balance = jiffies, \ .balance_interval = 1, \ diff --git a/include/linux/sched.h b/include/linux/sched.h index 1208feab46e..ea92e5c8908 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -648,6 +648,7 @@ enum idle_type #define SD_SHARE_CPUPOWER 128 /* Domain members share cpu power */ #define SD_POWERSAVINGS_BALANCE 256 /* Balance for power savings */ #define SD_SHARE_PKG_RESOURCES 512 /* Domain members share cpu pkg resources */ +#define SD_SERIALIZE 1024 /* Only a single load balancing instance */ #define BALANCE_FOR_MC_POWER \ (sched_smt_power_savings ? SD_POWERSAVINGS_BALANCE : 0) diff --git a/include/linux/topology.h b/include/linux/topology.h index b93bb6cc6cc..6c5a6e6e813 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -194,7 +194,8 @@ .wake_idx = 0, /* unused */ \ .forkexec_idx = 0, /* unused */ \ .per_cpu_gain = 100, \ - .flags = SD_LOAD_BALANCE, \ + .flags = SD_LOAD_BALANCE \ + | SD_SERIALIZE, \ .last_balance = jiffies, \ .balance_interval = 64, \ .nr_balance_failed = 0, \ diff --git a/kernel/sched.c b/kernel/sched.c index 0a4a26b21f6..2b2b780939c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2880,6 +2880,7 @@ static void update_load(struct rq *this_rq) * * Balancing parameters are set up in arch_init_sched_domains. */ +static DEFINE_SPINLOCK(balancing); static void run_rebalance_domains(struct softirq_action *h) { @@ -2909,6 +2910,11 @@ static void run_rebalance_domains(struct softirq_action *h) if (unlikely(!interval)) interval = 1; + if (sd->flags & SD_SERIALIZE) { + if (!spin_trylock(&balancing)) + goto out; + } + if (time_after_eq(jiffies, sd->last_balance + interval)) { if (load_balance(this_cpu, this_rq, sd, idle)) { /* @@ -2920,6 +2926,9 @@ static void run_rebalance_domains(struct softirq_action *h) } sd->last_balance = jiffies; } + if (sd->flags & SD_SERIALIZE) + spin_unlock(&balancing); +out: if (time_after(next_balance, sd->last_balance + interval)) next_balance = sd->last_balance + interval; }