From 4762b59f531d971fef9a5a8ccd3d02feb89621e0 Mon Sep 17 00:00:00 2001 From: Guo Hui Date: Wed, 19 Oct 2022 11:07:22 +0800 Subject: [PATCH] anolis: x86: paravirt: useless assignment instructions cause Unixbench full core performance degradation ANBZ: #2390 The instructions assigned to the vcpu_is_preempted function parameter in the X86 architecture physical machine are redundant instructions, causing the multi-core performance of Unixbench to drop by about 4% to 5%. The C function is as follows: static bool vcpu_is_preempted(long vcpu); The parameter 'vcpu' in the function osq_lock that calls the function vcpu_is_preempted is assigned as follows: The C code is in the function node_cpu: cpu = node->cpu - 1; The instructions corresponding to the C code are: mov 0x14(%rax),%edi sub $0x1,%edi The above instructions are unnecessary in the X86 Native operating environment, causing high cache-misses and degrading performance. This patch uses static_key to not execute this instruction in the Native runtime environment. The patch effect is as follows two machines, Unixbench runs with full core score: 1. Machine configuration: Intel(R) Xeon(R) Silver 4210 CPU @ 2.20GHz CPU core: 40 Memory: 256G OS Kernel: 4.19.90 Before using the patch: System Benchmarks Index Values BASELINE RESULT INDEX Dhrystone 2 using register variables 116700.0 948326591.2 81261.9 Double-Precision Whetstone 55.0 211986.3 38543.0 Execl Throughput 43.0 43453.2 10105.4 File Copy 1024 bufsize 2000 maxblocks 3960.0 438936.2 1108.4 File Copy 256 bufsize 500 maxblocks 1655.0 118197.4 714.2 File Copy 4096 bufsize 8000 maxblocks 5800.0 1534674.7 2646.0 Pipe Throughput 12440.0 46482107.6 37365.0 Pipe-based Context Switching 4000.0 1915094.2 4787.7 Process Creation 126.0 85442.2 6781.1 Shell Scripts (1 concurrent) 42.4 69400.7 16368.1 Shell Scripts (8 concurrent) 6.0 8877.2 14795.3 System Call Overhead 15000.0 4714906.1 3143.3 ======== System Benchmarks Index Score 7923.3 After using the patch: System Benchmarks Index Values BASELINE RESULT INDEX Dhrystone 2 using register variables 116700.0 947032915.5 81151.1 Double-Precision Whetstone 55.0 211971.2 38540.2 Execl Throughput 43.0 45054.8 10477.9 File Copy 1024 bufsize 2000 maxblocks 3960.0 515024.9 1300.6 File Copy 256 bufsize 500 maxblocks 1655.0 146354.6 884.3 File Copy 4096 bufsize 8000 maxblocks 5800.0 1679995.9 2896.5 Pipe Throughput 12440.0 46466394.2 37352.4 Pipe-based Context Switching 4000.0 1898221.4 4745.6 Process Creation 126.0 85653.1 6797.9 Shell Scripts (1 concurrent) 42.4 69437.3 16376.7 Shell Scripts (8 concurrent) 6.0 8898.9 14831.4 System Call Overhead 15000.0 4658746.7 3105.8 ======== System Benchmarks Index Score 8248.8 2. Machine configuration: Hygon C86 7185 32-core Processor CPU core: 128 Memory: 256G OS Kernel: 4.19.90 Before using the patch: System Benchmarks Index Values BASELINE RESULT INDEX Dhrystone 2 using register variables 116700.0 2256644068.3 193371.4 Double-Precision Whetstone 55.0 438969.9 79812.7 Execl Throughput 43.0 10108.6 2350.8 File Copy 1024 bufsize 2000 maxblocks 3960.0 275892.8 696.7 File Copy 256 bufsize 500 maxblocks 1655.0 72082.7 435.5 File Copy 4096 bufsize 8000 maxblocks 5800.0 925043.4 1594.9 Pipe Throughput 12440.0 118905512.5 95583.2 Pipe-based Context Switching 4000.0 7820945.7 19552.4 Process Creation 126.0 31233.3 2478.8 Shell Scripts (1 concurrent) 42.4 49042.8 11566.7 Shell Scripts (8 concurrent) 6.0 6656.0 11093.3 System Call Overhead 15000.0 6816047.5 4544.0 ======== System Benchmarks Index Score 7756.6 After using the patch: System Benchmarks Index Values BASELINE RESULT INDEX Dhrystone 2 using register variables 116700.0 2252272929.4 192996.8 Double-Precision Whetstone 55.0 451847.2 82154.0 Execl Throughput 43.0 10595.1 2464.0 File Copy 1024 bufsize 2000 maxblocks 3960.0 301279.3 760.8 File Copy 256 bufsize 500 maxblocks 1655.0 79291.3 479.1 File Copy 4096 bufsize 8000 maxblocks 5800.0 1039755.2 1792.7 Pipe Throughput 12440.0 118701468.1 95419.2 Pipe-based Context Switching 4000.0 8073453.3 20183.6 Process Creation 126.0 33440.9 2654.0 Shell Scripts (1 concurrent) 42.4 52722.6 12434.6 Shell Scripts (8 concurrent) 6.0 7050.4 11750.6 System Call Overhead 15000.0 6834371.5 4556.2 ======== System Benchmarks Index Score 8157.8 Signed-off-by: Guo Hui --- arch/x86/kernel/paravirt_patch_64.c | 3 +++ kernel/locking/mutex.c | 19 ++++++++++++++++++- kernel/locking/osq_lock.c | 19 ++++++++++++++++++- 3 files changed, 39 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c index 9cb98f7b07c9..a29fe9b89a3d 100644 --- a/arch/x86/kernel/paravirt_patch_64.c +++ b/arch/x86/kernel/paravirt_patch_64.c @@ -38,6 +38,8 @@ unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len) extern bool pv_is_native_spin_unlock(void); extern bool pv_is_native_vcpu_is_preempted(void); +DECLARE_STATIC_KEY_TRUE(vcpu_has_preemption); + unsigned native_patch(u8 type, u16 clobbers, void *ibuf, unsigned long addr, unsigned len) { @@ -73,6 +75,7 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, if (pv_is_native_vcpu_is_preempted()) { start = start_pv_lock_ops_vcpu_is_preempted; end = end_pv_lock_ops_vcpu_is_preempted; + static_branch_disable(&vcpu_has_preemption); goto patch_site; } goto patch_default; diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 3f8a35104285..7588ab788707 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -513,6 +513,23 @@ bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, return true; } +#ifdef vcpu_is_preempted +DECLARE_STATIC_KEY_TRUE(vcpu_has_preemption); + +static inline bool vcpu_is_preempted_node(struct task_struct *owner) +{ + if (static_branch_likely(&vcpu_has_preemption)) + return vcpu_is_preempted(task_cpu(owner)); + + return false; +} +#else +static inline bool vcpu_is_preempted_node(struct task_struct *owner) +{ + return false; +} +#endif + /* * Look out! "owner" is an entirely speculative pointer access and not * reliable. @@ -539,7 +556,7 @@ bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner, * Use vcpu_is_preempted to detect lock holder preemption issue. */ if (!owner->on_cpu || need_resched() || - vcpu_is_preempted(task_cpu(owner))) { + vcpu_is_preempted_node(owner)) { ret = false; break; } diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c index 6ef600aa0f47..5ecf7f00236c 100644 --- a/kernel/locking/osq_lock.c +++ b/kernel/locking/osq_lock.c @@ -27,6 +27,23 @@ static inline int node_cpu(struct optimistic_spin_node *node) return node->cpu - 1; } +#ifdef vcpu_is_preempted +DEFINE_STATIC_KEY_TRUE(vcpu_has_preemption); + +static inline bool vcpu_is_preempted_node(struct optimistic_spin_node *node) +{ + if (static_branch_likely(&vcpu_has_preemption)) + return vcpu_is_preempted(node_cpu(node->prev)); + + return false; +} +#else +static inline bool vcpu_is_preempted_node(struct optimistic_spin_node *node) +{ + return false; +} +#endif + static inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val) { int cpu_nr = encoded_cpu_val - 1; @@ -140,7 +157,7 @@ bool osq_lock(struct optimistic_spin_queue *lock) * Use vcpu_is_preempted() to avoid waiting for a preempted * lock holder: */ - if (need_resched() || vcpu_is_preempted(node_cpu(node->prev))) + if (need_resched() || vcpu_is_preempted_node(node)) goto unqueue; cpu_relax(); -- Gitee