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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-14 04:26:54 +07:00
e7c15cd8a1
The hardware latency tracer has been in the PREEMPT_RT patch for some time.
It is used to detect possible SMIs or any other hardware interruptions that
the kernel is unaware of. Note, NMIs may also be detected, but that may be
good to note as well.
The logic is pretty simple. It simply creates a thread that spins on a
single CPU for a specified amount of time (width) within a periodic window
(window). These numbers may be adjusted by their cooresponding names in
/sys/kernel/tracing/hwlat_detector/
The defaults are window = 1000000 us (1 second)
width = 500000 us (1/2 second)
The loop consists of:
t1 = trace_clock_local();
t2 = trace_clock_local();
Where trace_clock_local() is a variant of sched_clock().
The difference of t2 - t1 is recorded as the "inner" timestamp and also the
timestamp t1 - prev_t2 is recorded as the "outer" timestamp. If either of
these differences are greater than the time denoted in
/sys/kernel/tracing/tracing_thresh then it records the event.
When this tracer is started, and tracing_thresh is zero, it changes to the
default threshold of 10 us.
The hwlat tracer in the PREEMPT_RT patch was originally written by
Jon Masters. I have modified it quite a bit and turned it into a
tracer.
Based-on-code-by: Jon Masters <jcm@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
78 lines
2.6 KiB
Makefile
78 lines
2.6 KiB
Makefile
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# We are fully aware of the dangers of __builtin_return_address()
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FRAME_CFLAGS := $(call cc-disable-warning,frame-address)
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KBUILD_CFLAGS += $(FRAME_CFLAGS)
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# Do not instrument the tracer itself:
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ifdef CONFIG_FUNCTION_TRACER
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ORIG_CFLAGS := $(KBUILD_CFLAGS)
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KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
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ifdef CONFIG_FTRACE_SELFTEST
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# selftest needs instrumentation
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CFLAGS_trace_selftest_dynamic.o = $(CC_FLAGS_FTRACE)
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obj-y += trace_selftest_dynamic.o
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endif
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endif
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# If unlikely tracing is enabled, do not trace these files
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ifdef CONFIG_TRACING_BRANCHES
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KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
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endif
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CFLAGS_trace_benchmark.o := -I$(src)
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CFLAGS_trace_events_filter.o := -I$(src)
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obj-$(CONFIG_TRACE_CLOCK) += trace_clock.o
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obj-$(CONFIG_FUNCTION_TRACER) += libftrace.o
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obj-$(CONFIG_RING_BUFFER) += ring_buffer.o
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obj-$(CONFIG_RING_BUFFER_BENCHMARK) += ring_buffer_benchmark.o
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obj-$(CONFIG_TRACING) += trace.o
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obj-$(CONFIG_TRACING) += trace_output.o
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obj-$(CONFIG_TRACING) += trace_seq.o
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obj-$(CONFIG_TRACING) += trace_stat.o
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obj-$(CONFIG_TRACING) += trace_printk.o
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obj-$(CONFIG_TRACING_MAP) += tracing_map.o
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obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o
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obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
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obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o
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obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o
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obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
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obj-$(CONFIG_HWLAT_TRACER) += trace_hwlat.o
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obj-$(CONFIG_NOP_TRACER) += trace_nop.o
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obj-$(CONFIG_STACK_TRACER) += trace_stack.o
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obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
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obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += trace_functions_graph.o
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obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
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obj-$(CONFIG_BLK_DEV_IO_TRACE) += blktrace.o
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ifeq ($(CONFIG_BLOCK),y)
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obj-$(CONFIG_EVENT_TRACING) += blktrace.o
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endif
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obj-$(CONFIG_EVENT_TRACING) += trace_events.o
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obj-$(CONFIG_EVENT_TRACING) += trace_export.o
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obj-$(CONFIG_FTRACE_SYSCALLS) += trace_syscalls.o
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ifeq ($(CONFIG_PERF_EVENTS),y)
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obj-$(CONFIG_EVENT_TRACING) += trace_event_perf.o
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endif
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obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
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obj-$(CONFIG_EVENT_TRACING) += trace_events_trigger.o
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obj-$(CONFIG_HIST_TRIGGERS) += trace_events_hist.o
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obj-$(CONFIG_BPF_EVENTS) += bpf_trace.o
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obj-$(CONFIG_KPROBE_EVENT) += trace_kprobe.o
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obj-$(CONFIG_TRACEPOINTS) += power-traces.o
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ifeq ($(CONFIG_PM),y)
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obj-$(CONFIG_TRACEPOINTS) += rpm-traces.o
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endif
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ifeq ($(CONFIG_TRACING),y)
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obj-$(CONFIG_KGDB_KDB) += trace_kdb.o
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endif
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obj-$(CONFIG_PROBE_EVENTS) += trace_probe.o
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obj-$(CONFIG_UPROBE_EVENT) += trace_uprobe.o
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obj-$(CONFIG_TRACEPOINT_BENCHMARK) += trace_benchmark.o
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libftrace-y := ftrace.o
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