tracing: Clean up snapshot config logic and field name
cover tracing: Clean up snapshot config logic and field name
The latency tracers (scheduler, irqsoff, etc) were created when tracing was first added. These tracers required a "snapshot" buffer that was the same size as the ring buffer being written to. When a new max latency was hit, the main ring buffer would swap with the snapshot buffer so that the trace leading up to the latency would be saved in the snapshot buffer (The snapshot buffer is never written to directly and the data within it can be viewed without fear of being overwritten).
Later, a new feature was added to allow snapshots to be taken by user space or even event triggers. This created a "snapshot" file that allowed users to trigger a snapshot from user space to save the current trace.
The config for this new feature (CONFIG_TRACER_SNAPSHOT) would select the latency tracer config (CONFIG_TRACER_MAX_LATENCY) as it would need all the functionality from it as it already existed. But this was incorrect. As the snapshot feature is really what the latency tracers need and not the other way around.
Have CONFIG_TRACER_MAX_TRACE select CONFIG_TRACER_SNAPSHOT where the tracers that needs the max latency buffer selects the TRACE_MAX_TRACE which will then select TRACER_SNAPSHOT.
Also, go through trace.c and trace.h and make the code that only needs the TRACER_MAX_TRACE protected by that and the code that always requires the snapshot to be protected by TRACER_SNAPSHOT.
As this snapshot buffer now has a more generic use case, calling it "max_buffer" is confusing. Rename it to "snapshot_buffer".
Head SHA1: 5c478bf3c6e04e6699d66a98bc6cabcc8ef5391c
Steven Rostedt (2):
tracing: Better separate SNAPSHOT and MAX_TRACE options
tracing: Rename trace_array field max_buffer to snapshot_buffer
----
kernel/trace/Kconfig | 8 +-- kernel/trace/trace.c | 122 +++++++++++++++++++++--------------------- kernel/trace/trace.h | 24 +++++---- kernel/trace/trace_selftest.c | 10 ++-- 4 files changed, 84 insertions(+), 80 deletions(-)
PATCH 1/2 tracing: Better separate SNAPSHOT and MAX_TRACE options
From: Steven Rostedt <[email protected]>
The latency tracers (scheduler, irqsoff, etc) were created when tracing was first added. These tracers required a "snapshot" buffer that was the same size as the ring buffer being written to. When a new max latency was hit, the main ring buffer would swap with the snapshot buffer so that the trace leading up to the latency would be saved in the snapshot buffer (The snapshot buffer is never written to directly and the data within it can be viewed without fear of being overwritten).
Later, a new feature was added to allow snapshots to be taken by user space or even event triggers. This created a "snapshot" file that allowed users to trigger a snapshot from user space to save the current trace.
The config for this new feature (CONFIG_TRACER_SNAPSHOT) would select the latency tracer config (CONFIG_TRACER_MAX_LATENCY) as it would need all the functionality from it as it already existed. But this was incorrect. As the snapshot feature is really what the latency tracers need and not the other way around.
Have CONFIG_TRACER_MAX_TRACE select CONFIG_TRACER_SNAPSHOT where the tracers that needs the max latency buffer selects the TRACE_MAX_TRACE which will then select TRACER_SNAPSHOT.
Also, go through trace.c and trace.h and make the code that only needs the TRACER_MAX_TRACE protected by that and the code that always requires the snapshot to be protected by TRACER_SNAPSHOT.
Signed-off-by Steven Rostedt (Google) <[email protected]>
--- kernel/trace/Kconfig | 8 +++---- kernel/trace/trace.c | 50 ++++++++++++++++++++++---------------------- kernel/trace/trace.h | 11 ++++++---- 3 files changed, 36 insertions(+), 33 deletions(-)
kernel/trace/Kconfig +4 -4
@@ -133,6 +133,7 @@ config BUILDTIME_MCOUNT_SORT config TRACER_MAX_TRACE bool + select TRACER_SNAPSHOT config TRACE_CLOCK bool
@@ -422,7 +423,6 @@ config IRQSOFF_TRACER select GENERIC_TRACER select TRACER_MAX_TRACE select RING_BUFFER_ALLOW_SWAP - select TRACER_SNAPSHOT select TRACER_SNAPSHOT_PER_CPU_SWAP help This option measures the time spent in irqs-off critical
@@ -445,7 +445,6 @@ config PREEMPT_TRACER select GENERIC_TRACER select TRACER_MAX_TRACE select RING_BUFFER_ALLOW_SWAP - select TRACER_SNAPSHOT select TRACER_SNAPSHOT_PER_CPU_SWAP select TRACE_PREEMPT_TOGGLE help
@@ -467,7 +466,6 @@ config SCHED_TRACER select GENERIC_TRACER select CONTEXT_SWITCH_TRACER select TRACER_MAX_TRACE - select TRACER_SNAPSHOT help This tracer tracks the latency of the highest priority task to be scheduled in, starting from the point it has woken up.
@@ -617,7 +615,6 @@ config TRACE_SYSCALL_BUF_SIZE_DEFAULT config TRACER_SNAPSHOT bool "Create a snapshot trace buffer" - select TRACER_MAX_TRACE help Allow tracing users to take snapshot of the current buffer using the ftrace interface, e.g.:
@@ -625,6 +622,9 @@ config TRACER_SNAPSHOT echo 1 > /sys/kernel/tracing/snapshot cat snapshot + Note, the latency tracers select this option. To disable it, + all the latency tracers need to be disabled. + config TRACER_SNAPSHOT_PER_CPU_SWAP bool "Allow snapshot to swap per CPU" depends on TRACER_SNAPSHOT
kernel/trace/trace.c +25 -25
200 lines not on this page · raw message
kernel/trace/trace.h +7 -4
@@ -329,7 +329,7 @@ struct trace_array {struct list_head list;char *name;struct array_buffer array_buffer; -#ifdef CONFIG_TRACER_MAX_TRACE +#ifdef CONFIG_TRACER_SNAPSHOT /* * The max_buffer is used to snapshot the trace when a maximum * latency is reached, or when the user initiates a snapshot.
@@ -345,13 +345,16 @@ struct trace_array {bool allocated_snapshot;spinlock_t snapshot_trigger_lock;unsigned int snapshot; +#ifdef CONFIG_TRACER_MAX_TRACE unsigned long max_latency;#ifdef CONFIG_FSNOTIFY struct dentry *d_max_latency;struct work_struct fsnotify_work;struct irq_work fsnotify_irqwork; -#endif -#endif +#endif /* CONFIG_FSNOTIFY */ +#endif /* CONFIG_TRACER_MAX_TRACE */ +#endif /* CONFIG_TRACER_SNAPSHOT */ +/* The below is for memory mapped ring buffer */ unsigned int mapped;unsigned long range_addr_start;
@@ -377,7 +380,7 @@ struct trace_array {* * It is also used in other places outside the update_max_tr * so it needs to be defined outside of the -* CONFIG_TRACER_MAX_TRACE. +* CONFIG_TRACER_SNAPSHOT. */ arch_spinlock_t max_lock;#ifdef CONFIG_FTRACE_SYSCALLS
Signature · 1 line
2.51.0
PATCH 2/2 tracing: Rename trace_array field max_buffer to snapshot_buffer
In reply to Steven RostedtFrom: Steven Rostedt <[email protected]>
When tracing was first added, there were latency tracers that would take a snapshot of the current trace when a new max latency was hit. This snapshot buffer was called "max_buffer". Since then, a snapshot feature was added that allowed user space or event triggers to trigger a snapshot of the current buffer using the same max_buffer of the trace_array.
As this snapshot buffer now has a more generic use case, calling it "max_buffer" is confusing. Rename it to snapshot_buffer.
Signed-off-by Steven Rostedt (Google) <[email protected]>
--- kernel/trace/trace.c | 72 +++++++++++++++++------------------ kernel/trace/trace.h | 13 ++++--- kernel/trace/trace_selftest.c | 10 ++--- 3 files changed, 48 insertions(+), 47 deletions(-)
kernel/trace/trace.c +36 -36
@@ -934,12 +934,12 @@ int tracing_alloc_snapshot_instance(struct trace_array *tr)/* Make the snapshot buffer have the same order as main buffer */ order =ring_buffer_subbuf_order_get (tr->array_buffer.buffer); - ret =ring_buffer_subbuf_order_set (tr->max_buffer.buffer, order); + ret =ring_buffer_subbuf_order_set (tr->snapshot_buffer.buffer, order);if (ret <0 )return ret;/* allocate spare buffer */ - ret =resize_buffer_duplicate_size (&tr->max_buffer, + ret =resize_buffer_duplicate_size (&tr->snapshot_buffer, &tr->array_buffer,RING_BUFFER_ALL_CPUS );if (ret <0 )return ret;
@@ -957,10 +957,10 @@ static void free_snapshot(struct trace_array *tr)* The max_tr ring buffer has some state (e.g. ring->clock) and * we want preserve it. */ -ring_buffer_subbuf_order_set (tr->max_buffer.buffer,0 ); -ring_buffer_resize (tr->max_buffer.buffer,1 ,RING_BUFFER_ALL_CPUS ); -set_buffer_entries (&tr->max_buffer,1 ); -tracing_reset_online_cpus (&tr->max_buffer); +ring_buffer_subbuf_order_set (tr->snapshot_buffer.buffer,0 ); +ring_buffer_resize (tr->snapshot_buffer.buffer,1 ,RING_BUFFER_ALL_CPUS ); +set_buffer_entries (&tr->snapshot_buffer,1 ); +tracing_reset_online_cpus (&tr->snapshot_buffer); tr->allocated_snapshot = false; }
@@ -1562,7 +1562,7 @@ static void __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu) { struct array_buffer *trace_buf = &tr->array_buffer; -struct array_buffer *max_buf = &tr->max_buffer; +struct array_buffer *max_buf = &tr->snapshot_buffer;struct trace_array_cpu *data =per_cpu_ptr (trace_buf->data, cpu);struct trace_array_cpu *max_data =per_cpu_ptr (max_buf->data, cpu);
@@ -1622,9 +1622,9 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,/* Inherit the recordable setting from array_buffer */ if (ring_buffer_record_is_set_on (tr->array_buffer.buffer)) -ring_buffer_record_on (tr->max_buffer.buffer); +ring_buffer_record_on (tr->snapshot_buffer.buffer);else -ring_buffer_record_off (tr->max_buffer.buffer); +ring_buffer_record_off (tr->snapshot_buffer.buffer);#ifdef CONFIG_TRACER_SNAPSHOT if (tr->cond_snapshot && !tr->cond_snapshot->update (tr, cond_data)) {
@@ -1632,7 +1632,7 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu, return; }#endif -swap (tr->array_buffer.buffer, tr->max_buffer.buffer); +swap (tr->array_buffer.buffer, tr->snapshot_buffer.buffer);__update_max_tr (tr, tsk, cpu);
@@ -1667,7 +1667,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)arch_spin_lock (&tr->max_lock); - ret =ring_buffer_swap_cpu (tr->max_buffer.buffer, tr->array_buffer.buffer, cpu); + ret =ring_buffer_swap_cpu (tr->snapshot_buffer.buffer, tr->array_buffer.buffer, cpu);if (ret == -EBUSY ) {/*
@@ -1677,7 +1677,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)* and flag that it failed. * Another reason is resize is in progress. */ -trace_array_printk_buf (tr->max_buffer.buffer, _THIS_IP_, +trace_array_printk_buf (tr->snapshot_buffer.buffer, _THIS_IP_,"Failed to swap buffers due to commit or resize in progress\n" ); }
@@ -1726,7 +1726,7 @@ static int wait_on_pipe(struct trace_iterator *iter, int full)* to happen, this would now be the main buffer. */ if (iter->snapshot) - iter->array_buffer = &iter->tr->max_buffer; + iter->array_buffer = &iter->tr->snapshot_buffer;#endif return ret; }
@@ -1794,7 +1794,7 @@ static int run_tracer_selftest(struct tracer *type)if (type->use_max_tr) {/* If we expanded the buffers, make sure the max is expanded too */ if (tr->ring_buffer_expanded) -ring_buffer_resize (tr->max_buffer.buffer, trace_buf_size, +ring_buffer_resize (tr->snapshot_buffer.buffer, trace_buf_size,RING_BUFFER_ALL_CPUS ); tr->allocated_snapshot = true; }
@@ -1821,7 +1821,7 @@ static int run_tracer_selftest(struct tracer *type)/* Shrink the max buffer again */ if (tr->ring_buffer_expanded) -ring_buffer_resize (tr->max_buffer.buffer,1 , +ring_buffer_resize (tr->snapshot_buffer.buffer,1 , RING_BUFFER_ALL_CPUS); }#endif
@@ -2064,7 +2064,7 @@ void tracing_reset_all_online_cpus_unlocked(void) tr->clear_trace = false;tracing_reset_online_cpus (&tr->array_buffer);#ifdef CONFIG_TRACER_SNAPSHOT -tracing_reset_online_cpus (&tr->max_buffer); +tracing_reset_online_cpus (&tr->snapshot_buffer);#endif } }
@@ -2104,7 +2104,7 @@ static void tracing_start_tr(struct trace_array *tr)ring_buffer_record_enable (buffer);#ifdef CONFIG_TRACER_SNAPSHOT - buffer = tr->max_buffer.buffer; + buffer = tr->snapshot_buffer.buffer;if (buffer)ring_buffer_record_enable (buffer);#endif
@@ -2140,7 +2140,7 @@ static void tracing_stop_tr(struct trace_array *tr)ring_buffer_record_disable (buffer);#ifdef CONFIG_TRACER_SNAPSHOT - buffer = tr->max_buffer.buffer; + buffer = tr->snapshot_buffer.buffer;if (buffer)ring_buffer_record_disable (buffer);#endif
@@ -3947,7 +3947,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)#ifdef CONFIG_TRACER_SNAPSHOT /* Currently only the top directory has a snapshot */ if (tr->current_trace->print_max || snapshot) - iter->array_buffer = &tr->max_buffer; + iter->array_buffer = &tr->snapshot_buffer; else#endif iter->array_buffer = &tr->array_buffer;
@@ -4150,7 +4150,7 @@ static int tracing_open(struct inode *inode, struct file *file)#ifdef CONFIG_TRACER_MAX_TRACE if (tr->current_trace->print_max) - trace_buf = &tr->max_buffer; + trace_buf = &tr->snapshot_buffer;#endif if (cpu ==RING_BUFFER_ALL_CPUS )
@@ -4363,14 +4363,14 @@ int tracing_set_cpumask(struct trace_array *tr, !cpumask_test_cpu(cpu, tracing_cpumask_new)) {ring_buffer_record_disable_cpu (tr->array_buffer.buffer, cpu);#ifdef CONFIG_TRACER_SNAPSHOT -ring_buffer_record_disable_cpu (tr->max_buffer.buffer, cpu); +ring_buffer_record_disable_cpu (tr->snapshot_buffer.buffer, cpu);#endif }if (!cpumask_test_cpu (cpu, tr->tracing_cpumask) &&cpumask_test_cpu (cpu, tracing_cpumask_new)) {ring_buffer_record_enable_cpu (tr->array_buffer.buffer, cpu);#ifdef CONFIG_TRACER_SNAPSHOT -ring_buffer_record_enable_cpu (tr->max_buffer.buffer, cpu); +ring_buffer_record_enable_cpu (tr->snapshot_buffer.buffer, cpu);#endif } }
@@ -4580,7 +4580,7 @@ int set_tracer_flag(struct trace_array *tr, u64 mask, int enabled)case TRACE_ITER (OVERWRITE ):ring_buffer_change_overwrite (tr->array_buffer.buffer, enabled);#ifdef CONFIG_TRACER_SNAPSHOT -ring_buffer_change_overwrite (tr->max_buffer.buffer, enabled); +ring_buffer_change_overwrite (tr->snapshot_buffer.buffer, enabled);#endif break ;
@@ -5298,7 +5298,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,if (!tr->allocated_snapshot) goto out; - ret =ring_buffer_resize (tr->max_buffer.buffer, size, cpu); + ret =ring_buffer_resize (tr->snapshot_buffer.buffer, size, cpu);if (ret <0 ) {int r =resize_buffer_duplicate_size (&tr->array_buffer, &tr->array_buffer, cpu);
@@ -5323,7 +5323,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr, goto out_start; } -update_buffer_entries (&tr->max_buffer, cpu); +update_buffer_entries (&tr->snapshot_buffer, cpu); out:#endif /* CONFIG_TRACER_SNAPSHOT */
@@ -7040,9 +7040,9 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr)tracing_reset_online_cpus (&tr->array_buffer);#ifdef CONFIG_TRACER_SNAPSHOT -if (tr->max_buffer.buffer) -ring_buffer_set_clock (tr->max_buffer.buffer, trace_clocks[i].func); -tracing_reset_online_cpus (&tr->max_buffer); +if (tr->snapshot_buffer.buffer) +ring_buffer_set_clock (tr->snapshot_buffer.buffer, trace_clocks[i].func); +tracing_reset_online_cpus (&tr->snapshot_buffer);#endif if (tr->scratch && !(tr->flags &TRACE_ARRAY_FL_LAST_BOOT )) {
@@ -7174,7 +7174,7 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file) ret =0 ; iter->tr = tr; - iter->array_buffer = &tr->max_buffer; + iter->array_buffer = &tr->snapshot_buffer; iter->cpu_file =tracing_get_cpu (inode); m->private = iter; file->private_data = m;
@@ -7237,7 +7237,7 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,return -EINVAL ;#endif if (tr->allocated_snapshot) - ret =resize_buffer_duplicate_size (&tr->max_buffer, + ret =resize_buffer_duplicate_size (&tr->snapshot_buffer, &tr->array_buffer, iter->cpu_file); ret =tracing_arm_snapshot_locked (tr);
@@ -7258,9 +7258,9 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,default :if (tr->allocated_snapshot) {if (iter->cpu_file ==RING_BUFFER_ALL_CPUS ) -tracing_reset_online_cpus (&tr->max_buffer); +tracing_reset_online_cpus (&tr->snapshot_buffer);else -tracing_reset_cpu (&tr->max_buffer, iter->cpu_file); +tracing_reset_cpu (&tr->snapshot_buffer, iter->cpu_file); }break ; }
@@ -7316,7 +7316,7 @@ static int snapshot_raw_open(struct inode *inode, struct file *filp) } info->iter.snapshot = true; - info->iter.array_buffer = &info->iter.tr->max_buffer; + info->iter.array_buffer = &info->iter.tr->snapshot_buffer;return ret; }
@@ -9199,7 +9199,7 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf,if (!tr->allocated_snapshot) goto out_max; - ret =ring_buffer_subbuf_order_set (tr->max_buffer.buffer, order); + ret =ring_buffer_subbuf_order_set (tr->snapshot_buffer.buffer, order);if (ret) {/* Put back the old order */ cnt =ring_buffer_subbuf_order_set (tr->array_buffer.buffer, old_order);
@@ -9420,7 +9420,7 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)if (tr->range_addr_start)return 0 ; - ret =allocate_trace_buffer (tr, &tr->max_buffer, + ret =allocate_trace_buffer (tr, &tr->snapshot_buffer, allocate_snapshot ? size :1 );if (MEM_FAIL (ret,"Failed to allocate trace buffer\n" )) {free_trace_buffer (&tr->array_buffer);
@@ -9443,7 +9443,7 @@ static void free_trace_buffers(struct trace_array *tr)kfree (tr->module_delta);#ifdef CONFIG_TRACER_SNAPSHOT -free_trace_buffer (&tr->max_buffer); +free_trace_buffer (&tr->snapshot_buffer);#endif }
kernel/trace/trace.h +7 -6
@@ -331,17 +331,18 @@ struct trace_array {struct array_buffer array_buffer;#ifdef CONFIG_TRACER_SNAPSHOT /* -* The max_buffer is used to snapshot the trace when a maximum +* The snapshot_buffer is used to snapshot the trace when a maximum * latency is reached, or when the user initiates a snapshot. * Some tracers will use this to store a maximum trace while * it continues examining live traces. * -* The buffers for the max_buffer are set up the same as the array_buffer -* When a snapshot is taken, the buffer of the max_buffer is swapped -* with the buffer of the array_buffer and the buffers are reset for -* the array_buffer so the tracing can continue. +* The buffers for the snapshot_buffer are set up the same as the +* array_buffer. When a snapshot is taken, the buffer of the +* snapshot_buffer is swapped with the buffer of the array_buffer +* and the buffers are reset for the array_buffer so the tracing can +* continue. */ -struct array_buffer max_buffer; +struct array_buffer snapshot_buffer;bool allocated_snapshot;spinlock_t snapshot_trigger_lock;unsigned int snapshot;
kernel/trace/trace_selftest.c +5 -5
@@ -1225,7 +1225,7 @@ trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)/* check both trace buffers */ ret =trace_test_buffer (&tr->array_buffer,NULL );if (!ret) - ret =trace_test_buffer (&tr->max_buffer, &count); + ret =trace_test_buffer (&tr->snapshot_buffer, &count); trace->reset (tr);tracing_start ();
@@ -1287,7 +1287,7 @@ trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr)/* check both trace buffers */ ret =trace_test_buffer (&tr->array_buffer,NULL );if (!ret) - ret =trace_test_buffer (&tr->max_buffer, &count); + ret =trace_test_buffer (&tr->snapshot_buffer, &count); trace->reset (tr);tracing_start ();
@@ -1355,7 +1355,7 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *if (ret) goto out; - ret =trace_test_buffer (&tr->max_buffer, &count); + ret =trace_test_buffer (&tr->snapshot_buffer, &count);if (ret) goto out;
@@ -1385,7 +1385,7 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *if (ret) goto out; - ret =trace_test_buffer (&tr->max_buffer, &count); + ret =trace_test_buffer (&tr->snapshot_buffer, &count);if (!ret && !count) {printk (KERN_CONT ".. no entries found .." );
@@ -1513,7 +1513,7 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)/* check both trace buffers */ ret =trace_test_buffer (&tr->array_buffer,NULL );if (!ret) - ret =trace_test_buffer (&tr->max_buffer, &count); + ret =trace_test_buffer (&tr->snapshot_buffer, &count); trace->reset (tr);
Signature · 1 line
2.51.0