Messages in this thread Patch in this message | | | Date | Thu, 17 Aug 2023 10:57:25 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | RFE: perf lock contention --bpf on an RT kernel |
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Hi Namhyung, I noticed this when trying to use the BPF mode of perf lock contention on an RT kernel:
[root@nine perf-tools-next]# perf lock contention -ba libbpf: prog 'contention_begin': BPF program load failed: Invalid argument libbpf: prog 'contention_begin': -- BEGIN PROG LOAD LOG -- R1 type=ctx expected=fp 0: R1=ctx(off=0,imm=0) R10=fp0 ; int contention_begin(u64 *ctx) 0: (bf) r7 = r1 ; R1=ctx(off=0,imm=0) R7_w=ctx(off=0,imm=0) ; if (!enabled || !can_record(ctx)) 1: (18) r1 = 0xffffc077c0322000 ; R1_w=map_value(off=0,ks=4,vs=60,imm=0) 3: (61) r1 = *(u32 *)(r1 +0) ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (!enabled || !can_record(ctx)) 4: (15) if r1 == 0x0 goto pc+209 ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (has_cpu) { 5: (18) r1 = 0xffffc077c0322028 ; R1_w=map_value(off=40,ks=4,vs=60,imm=0) 7: (61) r1 = *(u32 *)(r1 +0) ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (has_cpu) { 8: (15) if r1 == 0x0 goto pc+8 ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; __u32 cpu = bpf_get_smp_processor_id(); 9: (85) call bpf_get_smp_processor_id#8 ; R0=scalar() ; __u32 cpu = bpf_get_smp_processor_id(); 10: (63) *(u32 *)(r10 -32) = r0 ; R0=scalar() R10=fp0 fp-32=????mmmm 11: (bf) r2 = r10 ; R2_w=fp0 R10=fp0 ; __u32 cpu = bpf_get_smp_processor_id(); 12: (07) r2 += -32 ; R2_w=fp-32 ; ok = bpf_map_lookup_elem(&cpu_filter, &cpu); 13: (18) r1 = 0xffff9f260667b800 ; R1_w=map_ptr(off=0,ks=4,vs=1,imm=0) 15: (85) call bpf_map_lookup_elem#1 ; R0_w=map_value_or_null(id=1,off=0,ks=4,vs=1,imm=0) 16: (15) if r0 == 0x0 goto pc+197 ; R0_w=map_value(off=0,ks=4,vs=1,imm=0) ; if (has_task) { 17: (18) r1 = 0xffffc077c032202c ; R1_w=map_value(off=44,ks=4,vs=60,imm=0) 19: (61) r1 = *(u32 *)(r1 +0) ; R1=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (has_task) { 20: (15) if r1 == 0x0 goto pc+8 ; R1=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; __u32 pid = bpf_get_current_pid_tgid(); 21: (85) call bpf_get_current_pid_tgid#14 ; R0_w=scalar() ; __u32 pid = bpf_get_current_pid_tgid(); 22: (63) *(u32 *)(r10 -32) = r0 ; R0_w=scalar() R10=fp0 fp-32=????mmmm 23: (bf) r2 = r10 ; R2_w=fp0 R10=fp0 ; __u32 pid = bpf_get_current_pid_tgid(); 24: (07) r2 += -32 ; R2_w=fp-32 ; ok = bpf_map_lookup_elem(&task_filter, &pid); 25: (18) r1 = 0xffff9f260667b400 ; R1_w=map_ptr(off=0,ks=4,vs=1,imm=0) 27: (85) call bpf_map_lookup_elem#1 ; R0_w=map_value_or_null(id=2,off=0,ks=4,vs=1,imm=0) 28: (15) if r0 == 0x0 goto pc+185 ; R0_w=map_value(off=0,ks=4,vs=1,imm=0) ; if (has_type) { 29: (18) r1 = 0xffffc077c0322030 ; R1_w=map_value(off=48,ks=4,vs=60,imm=0) 31: (61) r1 = *(u32 *)(r1 +0) ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (has_type) { 32: (15) if r1 == 0x0 goto pc+8 ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; __u32 flags = (__u32)ctx[1]; 33: (79) r1 = *(u64 *)(r7 +8) ; R1_w=scalar() R7=ctx(off=0,imm=0) ; __u32 flags = (__u32)ctx[1]; 34: (63) *(u32 *)(r10 -32) = r1 ; R1_w=scalar() R10=fp0 fp-32=????mmmm 35: (bf) r2 = r10 ; R2_w=fp0 R10=fp0 ; __u32 flags = (__u32)ctx[1]; 36: (07) r2 += -32 ; R2_w=fp-32 ; ok = bpf_map_lookup_elem(&type_filter, &flags); 37: (18) r1 = 0xffff9f260667b000 ; R1_w=map_ptr(off=0,ks=4,vs=1,imm=0) 39: (85) call bpf_map_lookup_elem#1 ; R0=map_value_or_null(id=3,off=0,ks=4,vs=1,imm=0) 40: (15) if r0 == 0x0 goto pc+173 ; R0=map_value(off=0,ks=4,vs=1,imm=0) ; if (has_addr) { 41: (18) r1 = 0xffffc077c0322034 ; R1_w=map_value(off=52,ks=4,vs=60,imm=0) 43: (61) r1 = *(u32 *)(r1 +0) ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (has_addr) { 44: (15) if r1 == 0x0 goto pc+8 ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; __u64 addr = ctx[0]; 45: (79) r1 = *(u64 *)(r7 +0) ; R1_w=scalar() R7=ctx(off=0,imm=0) ; __u64 addr = ctx[0]; 46: (7b) *(u64 *)(r10 -32) = r1 ; R1_w=scalar() R10=fp0 fp-32_w=mmmmmmmm 47: (bf) r2 = r10 ; R2_w=fp0 R10=fp0 ; __u64 addr = ctx[0]; 48: (07) r2 += -32 ; R2_w=fp-32 ; ok = bpf_map_lookup_elem(&addr_filter, &addr); 49: (18) r1 = 0xffff9f260667f400 ; R1_w=map_ptr(off=0,ks=8,vs=1,imm=0) 51: (85) call bpf_map_lookup_elem#1 ; R0=map_value_or_null(id=4,off=0,ks=8,vs=1,imm=0) ; if (!enabled || !can_record(ctx)) 52: (15) if r0 == 0x0 goto pc+161 ; R0=map_value(off=0,ks=8,vs=1,imm=0) ; pid = bpf_get_current_pid_tgid(); 53: (85) call bpf_get_current_pid_tgid#14 ; R0_w=scalar() ; pid = bpf_get_current_pid_tgid(); 54: (63) *(u32 *)(r10 -8) = r0 ; R0_w=scalar() R10=fp0 fp-8=????mmmm 55: (bf) r2 = r10 ; R2_w=fp0 R10=fp0 ; pid = bpf_get_current_pid_tgid(); 56: (07) r2 += -8 ; R2_w=fp-8 ; pelem = bpf_map_lookup_elem(&tstamp, &pid); 57: (18) r1 = 0xffff9f260667a800 ; R1_w=map_ptr(off=0,ks=4,vs=24,imm=0) 59: (85) call bpf_map_lookup_elem#1 ; R0_w=map_value_or_null(id=5,off=0,ks=4,vs=24,imm=0) 60: (bf) r6 = r0 ; R0=map_value_or_null(id=5,off=0,ks=4,vs=24,imm=0) R6=map_value_or_null(id=5,off=0,ks=4,vs=24,imm=0) ; if (pelem && pelem->lock) 61: (15) if r6 == 0x0 goto pc+32 ; R6=map_value(off=0,ks=4,vs=24,imm=0) ; if (pelem && pelem->lock) 62: (79) r1 = *(u64 *)(r6 +8) ; R1_w=scalar() R6=map_value(off=0,ks=4,vs=24,imm=0) ; if (pelem && pelem->lock) 63: (15) if r1 == 0x0 goto pc+1 65: R0=map_value(off=0,ks=4,vs=24,imm=0) R1_w=0 R6=map_value(off=0,ks=4,vs=24,imm=0) R7=ctx(off=0,imm=0) R10=fp0 fp-8=????mmmm fp-32=mmmmmmmm ; pelem->timestamp = bpf_ktime_get_ns(); 65: (85) call bpf_ktime_get_ns#5 ; R0_w=scalar() ; pelem->timestamp = bpf_ktime_get_ns(); 66: (7b) *(u64 *)(r6 +0) = r0 ; R0_w=scalar() R6=map_value(off=0,ks=4,vs=24,imm=0) ; pelem->lock = (__u64)ctx[0]; 67: (79) r3 = *(u64 *)(r7 +0) ; R3_w=scalar() R7=ctx(off=0,imm=0) ; pelem->lock = (__u64)ctx[0]; 68: (7b) *(u64 *)(r6 +8) = r3 ; R3_w=scalar() R6=map_value(off=0,ks=4,vs=24,imm=0) ; pelem->flags = (__u32)ctx[1]; 69: (79) r1 = *(u64 *)(r7 +8) ; R1_w=scalar() R7=ctx(off=0,imm=0) ; pelem->flags = (__u32)ctx[1]; 70: (63) *(u32 *)(r6 +16) = r1 ; R1_w=scalar() R6=map_value(off=0,ks=4,vs=24,imm=0) ; if (needs_callstack) { 71: (18) r2 = 0xffffc077c0322008 ; R2_w=map_value(off=8,ks=4,vs=60,imm=0) 73: (61) r2 = *(u32 *)(r2 +0) ; R2=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (needs_callstack) { 74: (15) if r2 == 0x0 goto pc+43 118: R0=scalar() R1=scalar() R2=0 R3=scalar() R6=map_value(off=0,ks=4,vs=24,imm=0) R7=ctx(off=0,imm=0) R10=fp0 fp-8=????mmmm fp-32=mmmmmmmm ; } else if (aggr_mode == LOCK_AGGR_TASK) { 118: (18) r2 = 0xffffc077c0322014 ; R2_w=map_value(off=20,ks=4,vs=60,imm=0) 120: (61) r2 = *(u32 *)(r2 +0) ; R2_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; } else if (aggr_mode == LOCK_AGGR_TASK) { 121: (55) if r2 != 0x1 goto pc+92 ; R2_w=1 ; if (lock_owner) { 122: (18) r2 = 0xffffc077c0322018 ; R2_w=map_value(off=24,ks=4,vs=60,imm=0) 124: (61) r2 = *(u32 *)(r2 +0) ; R2=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (lock_owner) { 125: (15) if r2 == 0x0 goto pc+34 ; R2=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) ; if (flags & LCB_F_MUTEX) { 126: (bf) r2 = r1 ; R1=scalar(id=6) R2_w=scalar(id=6) 127: (57) r2 &= 32 ; R2_w=scalar(umax=32,var_off=(0x0; 0x20)) ; if (flags & LCB_F_MUTEX) { 128: (15) if r2 == 0x0 goto pc+2 ; R2_w=scalar(umax=32,var_off=(0x0; 0x20)) 129: <invalid CO-RE relocation> failed to resolve CO-RE relocation <byte_off> [47] struct mutex.owner.counter (0:0:0 @ offset 0) processed 95 insns (limit 1000000) max_states_per_insn 0 total_states 10 peak_states 10 mark_read 4 -- END PROG LOAD LOG -- libbpf: prog 'contention_begin': failed to load: -22 libbpf: failed to load object 'lock_contention_bpf' libbpf: failed to load BPF skeleton 'lock_contention_bpf': -22 Failed to load lock-contention BPF skeleton lock contention BPF setup failed [root@nine perf-tools-next]# uname -r 5.14.0-284.18.1.rt14.303.el9_2.x86_64 [root@nine perf-tools-next]# pahole mutex struct mutex { struct rt_mutex_base rtmutex; /* 0 32 */
/* size: 32, cachelines: 1, members: 1 */ /* last cacheline: 32 bytes */ }; [root@nine perf-tools-next]# pahole -E mutex struct mutex { struct rt_mutex_base { /* typedef raw_spinlock_t */ struct raw_spinlock { /* typedef arch_spinlock_t */ struct qspinlock { union { /* typedef atomic_t */ struct { int counter; /* 0 4 */ } val; /* 0 4 */ struct { /* typedef u8 -> __u8 */ unsigned char locked; /* 0 1 */ /* typedef u8 -> __u8 */ unsigned char pending; /* 1 1 */ }; /* 0 2 */ struct { /* typedef u16 -> __u16 */ short unsigned int locked_pending; /* 0 2 */ /* typedef u16 -> __u16 */ short unsigned int tail; /* 2 2 */ }; /* 0 4 */ }; /* 0 4 */ } raw_lock; /* 0 4 */ } wait_lock; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
struct rb_root_cached { struct rb_root { struct rb_node * rb_node; /* 8 8 */ }rb_root; /* 8 8 */ struct rb_node * rb_leftmost; /* 16 8 */ }waiters; /* 8 16 */ struct task_struct * owner; /* 24 8 */ }rtmutex; /* 0 32 */
/* size: 32, cachelines: 1, members: 1 */ /* last cacheline: 32 bytes */ }; [root@nine perf-tools-next]# uname -r 5.14.0-284.18.1.rt14.303.el9_2.x86_64 [root@nine perf-tools-next]#
So we need some extra logic to get at the mutex owner...
[root@nine perf-tools-next]# ls -la /sys/kernel/debug/tracing/events/lock/ contention_begin/ contention_end/ enable filter [root@nine perf-tools-next]# ls -la /sys/kernel/debug/tracing/events/lock/ total 0 drwxr-xr-x. 4 root root 0 Aug 17 08:44 . drwxr-xr-x. 114 root root 0 Aug 17 08:45 .. drwxr-xr-x. 2 root root 0 Aug 17 08:44 contention_begin drwxr-xr-x. 2 root root 0 Aug 17 08:44 contention_end -rw-r-----. 1 root root 0 Aug 17 08:44 enable -rw-r-----. 1 root root 0 Aug 17 08:44 filter [root@nine perf-tools-next]#
I tried up to now the following patch, it loads, but produces no output :-\
diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c index 8d3cfbb3cc65..8b65391401a5 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -100,6 +100,18 @@ struct rw_semaphore___new { atomic_long_t owner; } __attribute__((preserve_access_index)); +struct rw_semaphore___rt { + struct rwbase_rt { + struct rt_mutex_base { + struct task_struct *owner; + } rtmutex; + } rwbase; +} __attribute__((preserve_access_index)); + +struct mutex___rt { + struct rt_mutex_base rtmutex; +} __attribute__((preserve_access_index)); + struct mm_struct___old { struct rw_semaphore mmap_sem; } __attribute__((preserve_access_index)); @@ -202,8 +214,19 @@ static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags) __u64 owner = 0; if (flags & LCB_F_MUTEX) { +#if __has_builtin(__builtin_preserve_type_info) && __clang_major__ >= 15 + if (bpf_core_type_matches(struct mutex___rt)) { + struct mutex___rt *mutex = (void *)lock; + owner = (unsigned long)BPF_CORE_READ(mutex, rtmutex.owner); + } else if (bpf_core_type_matches(struct mutex)) { + struct mutex *mutex = (void *)lock; + owner = BPF_CORE_READ(mutex, owner.counter); + } +#else + /* assume non-RT struct */ struct mutex *mutex = (void *)lock; owner = BPF_CORE_READ(mutex, owner.counter); +#endif } else if (flags == LCB_F_READ || flags == LCB_F_WRITE) { /* * Support for the BPF_TYPE_MATCHES argument to the @@ -218,6 +241,9 @@ static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags) } else if (bpf_core_type_matches(struct rw_semaphore___new)) { struct rw_semaphore___new *rwsem = (void *)lock; owner = BPF_CORE_READ(rwsem, owner.counter); + } else if (bpf_core_type_matches(struct rw_semaphore___rt)) { + struct rw_semaphore___rt *rwsem = (void *)lock; + owner = (unsigned long)BPF_CORE_READ(rwsem, rwbase.rtmutex.owner); } #else /* assume new struct */
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