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[PATCH 4.9 61/72] Revert "sched/core: Optimize SCHED_SMT"

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.9 61/72] Revert "sched/core: Optimize SCHED_SMT"
Date 2017-07-19 12:30 +0200
Message-ID <u4Up0-7eW-111@gated-at.bofh.it> (permalink)
References <u4UoV-7eW-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit 1b568f0aabf280555125bc7cefc08321ff0ebaba.

For the 4.9 kernel tree, this patch causes scheduler regressions.  It is
fixed in newer kernels with a large number of individual patches, the
sum of which is too big for the stable kernel tree.

Ingo recommended just reverting the single patch for this tree, as it's
much simpler.

Reported-by: Ben Guthro <ben@guthro.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/sched/core.c  |   19 -------------------
 kernel/sched/fair.c  |    8 +-------
 kernel/sched/sched.h |   23 ++++++-----------------
 3 files changed, 7 insertions(+), 43 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7422,22 +7422,6 @@ int sched_cpu_dying(unsigned int cpu)
 }
 #endif
 
-#ifdef CONFIG_SCHED_SMT
-DEFINE_STATIC_KEY_FALSE(sched_smt_present);
-
-static void sched_init_smt(void)
-{
-	/*
-	 * We've enumerated all CPUs and will assume that if any CPU
-	 * has SMT siblings, CPU0 will too.
-	 */
-	if (cpumask_weight(cpu_smt_mask(0)) > 1)
-		static_branch_enable(&sched_smt_present);
-}
-#else
-static inline void sched_init_smt(void) { }
-#endif
-
 void __init sched_init_smp(void)
 {
 	cpumask_var_t non_isolated_cpus;
@@ -7467,9 +7451,6 @@ void __init sched_init_smp(void)
 
 	init_sched_rt_class();
 	init_sched_dl_class();
-
-	sched_init_smt();
-
 	sched_smp_initialized = true;
 }
 
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5376,7 +5376,7 @@ static inline bool test_idle_cores(int c
  * Since SMT siblings share all cache levels, inspecting this limited remote
  * state should be fairly cheap.
  */
-void __update_idle_core(struct rq *rq)
+void update_idle_core(struct rq *rq)
 {
 	int core = cpu_of(rq);
 	int cpu;
@@ -5408,9 +5408,6 @@ static int select_idle_core(struct task_
 	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
 	int core, cpu, wrap;
 
-	if (!static_branch_likely(&sched_smt_present))
-		return -1;
-
 	if (!test_idle_cores(target, false))
 		return -1;
 
@@ -5444,9 +5441,6 @@ static int select_idle_smt(struct task_s
 {
 	int cpu;
 
-	if (!static_branch_likely(&sched_smt_present))
-		return -1;
-
 	for_each_cpu(cpu, cpu_smt_mask(target)) {
 		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
 			continue;
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -43,6 +43,12 @@ extern void cpu_load_update_active(struc
 static inline void cpu_load_update_active(struct rq *this_rq) { }
 #endif
 
+#ifdef CONFIG_SCHED_SMT
+extern void update_idle_core(struct rq *rq);
+#else
+static inline void update_idle_core(struct rq *rq) { }
+#endif
+
 /*
  * Helpers for converting nanosecond timing to jiffy resolution
  */
@@ -731,23 +737,6 @@ static inline int cpu_of(struct rq *rq)
 #endif
 }
 
-
-#ifdef CONFIG_SCHED_SMT
-
-extern struct static_key_false sched_smt_present;
-
-extern void __update_idle_core(struct rq *rq);
-
-static inline void update_idle_core(struct rq *rq)
-{
-	if (static_branch_unlikely(&sched_smt_present))
-		__update_idle_core(rq);
-}
-
-#else
-static inline void update_idle_core(struct rq *rq) { }
-#endif
-
 DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 
 #define cpu_rq(cpu)		(&per_cpu(runqueues, (cpu)))

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[PATCH 4.9 00/72] 4.9.39-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 62/72] sched/fair, cpumask: Export for_each_cpu_wrap() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 58/72] crypto: sha1-ssse3 - Disable avx2 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 30/72] irqchip/gic-v3: Fix out-of-bound access in gic_set_affinity Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 36/72] thp, mm: fix crash due race in MADV_FREE handling Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 28/72] cfg80211: Check if PMKID attribute is of expected size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 48/72] vt: fix unchecked __put_user() in tioclinux ioctls Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 32/72] parisc: use compat_sys_keyctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 57/72] crypto: atmel - only treat EBUSY as transient if backlog Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 65/72] sched/topology: Fix overlapping sched_group_mask Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 43/72] arm64: move ELF_ET_DYN_BASE to 4GB / 4MB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 72/72] kvm: vmx: allow host to access guest MSR_IA32_BNDCFGS Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 03/72] net: sched: Fix one possible panic when no destroy callback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 53/72] mnt: Make propagate_umount less slow for overlapping mount propagation trees Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 46/72] exec: Limit arg stack to at most 75% of _STK_LIM Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 09/72] bridge: mdb: fix leak on complete_info ptr on fail path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 04/72] net/phy: micrel: configure intterupts after autoneg workaround Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 66/72] PM / wakeirq: Convert to SRCU Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 68/72] tracing: Use SOFTIRQ_OFFSET for softirq dectection for more accurate results Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 15/72] net/mlx5e: Fix TX carrier errors report in get stats ndo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 10/72] rocker: move dereference before free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 39/72] fs/dcache.c: fix spin lockup issue on nlru->lock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 11/72] bpf: prevent leaking pointer via xadd on unpriviledged Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 17/72] vxlan: fix hlist corruption Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 61/72] Revert "sched/core: Optimize SCHED_SMT" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:30 +0200
  [PATCH 4.9 33/72] parisc: DMA API: return error instead of BUG_ON for dma ops on non dma devs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 38/72] mm/list_lru.c: fix list_lru_count_node() to be race free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 49/72] rcu: Add memory barriers for NOCB leader wakeup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 41/72] binfmt_elf: use ELF_ET_DYN_BASE only for PIE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 54/72] selftests/capabilities: Fix the test_execve test Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 50/72] nvmem: core: fix leaks on registration errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 29/72] cfg80211: Check if NAN service ID is of expected size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 45/72] s390: reduce ELF_ET_DYN_BASE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 31/72] parisc: Report SIGSEGV instead of SIGBUS when running out of stack Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 42/72] arm: move ELF_ET_DYN_BASE to 4MB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 47/72] ARM64: dts: marvell: armada37xx: Fix timer interrupt specifiers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 16/72] ipv6: dad: dont remove dynamic addresses if link is down Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 51/72] mnt: In umount propagation reparent in a separate pass Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 64/72] sched/topology: Optimize build_group_mask() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 18/72] net: core: Fix slab-out-of-bounds in netdev_stats_to_stats64 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 14/72] liquidio: fix bug in soft reset failure detection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 35/72] tools/lib/lockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain/: Depth Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 44/72] powerpc: move ELF_ET_DYN_BASE to 4GB / 4MB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 20/72] vrf: fix bug_on triggered by rx when destroying a vrf Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 27/72] cfg80211: Validate frequencies nested in NL80211_ATTR_SCAN_FREQUENCIES Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 26/72] cfg80211: Define nla_policy for NL80211_ATTR_LOCAL_MESH_POWER_MODE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 52/72] mnt: In propgate_umount handle visiting mounts in any order Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 37/72] kernel/extable.c: mark core_kernel_text notrace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 25/72] sfc: dont read beyond unicast address list Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 63/72] sched/topology: Fix building of overlapping sched-groups Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 34/72] parisc/mm: Ensure IRQs are off in switch_mm() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 40/72] checkpatch: silence perl 5.26.0 unescaped left brace warnings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 24/72] brcmfmac: Fix glom_skb leak in brcmf_sdiod_recv_chain Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:40 +0200
  [PATCH 4.9 01/72] xen-netfront: Rework the fix for Rx stall during OOM and network stress Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  [PATCH 4.9 13/72] net/mlx5: Cancel delayed recovery work when unloading the driver Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  [PATCH 4.9 21/72] rds: tcp: use sock_create_lite() to create the accept socket Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  [PATCH 4.9 02/72] net_sched: fix error recovery at qdisc creation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  [PATCH 4.9 05/72] ipv6: avoid unregistering inet6_dev for loopback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  [PATCH 4.9 06/72] net: dp83640: Avoid NULL pointer dereference. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  [PATCH 4.9 08/72] net: prevent sign extension in dev_get_stats() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  [PATCH 4.9 23/72] brcmfmac: Fix a memory leak in error handling path in brcmf_cfg80211_attach Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-19 12:50 +0200
  Re: [PATCH 4.9 00/72] 4.9.39-stable review Sumit Semwal <sumit.semwal@linaro.org> - 2017-07-19 18:00 +0200
    Re: [PATCH 4.9 00/72] 4.9.39-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-07-20 07:10 +0200
  Re: [PATCH 4.9 00/72] 4.9.39-stable review Guenter Roeck <linux@roeck-us.net> - 2017-07-19 22:40 +0200
  Re: [PATCH 4.9 00/72] 4.9.39-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-07-20 01:40 +0200

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