d769041f86
The old "lock always" scheme had issues with lockdep, and was not very
efficient anyways.
This patch does a new design to be partially lockless on writes.
Writes will add new entries to the per cpu pages by simply disabling
interrupts. When a write needs to go to another page than it will
grab the lock.
A new "read page" has been added so that the reader can pull out a page
from the ring buffer to read without worrying about the writer writing over
it. This allows us to not take the lock for all reads. The lock is
now only taken when a read needs to go to a new page.
This is far from lockless, and interrupts still need to be disabled,
but it is a step towards a more lockless solution, and it also
solves a lot of the issues that were noticed by the first conversion
of ftrace to the ring buffers.
Note: the ring_buffer_{un}lock API has been removed.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
127 lines
3.8 KiB
C
127 lines
3.8 KiB
C
#ifndef _LINUX_RING_BUFFER_H
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#define _LINUX_RING_BUFFER_H
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#include <linux/mm.h>
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#include <linux/seq_file.h>
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struct ring_buffer;
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struct ring_buffer_iter;
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/*
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* Don't reference this struct directly, use functions below.
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*/
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struct ring_buffer_event {
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u32 type:2, len:3, time_delta:27;
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u32 array[];
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};
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/**
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* enum ring_buffer_type - internal ring buffer types
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*
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* @RINGBUF_TYPE_PADDING: Left over page padding
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* array is ignored
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* size is variable depending on how much
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* padding is needed
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*
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* @RINGBUF_TYPE_TIME_EXTEND: Extend the time delta
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* array[0] = time delta (28 .. 59)
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* size = 8 bytes
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*
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* @RINGBUF_TYPE_TIME_STAMP: Sync time stamp with external clock
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* array[0] = tv_nsec
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* array[1] = tv_sec
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* size = 16 bytes
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*
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* @RINGBUF_TYPE_DATA: Data record
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* If len is zero:
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* array[0] holds the actual length
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* array[1..(length+3)/4-1] holds data
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* else
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* length = len << 2
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* array[0..(length+3)/4] holds data
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*/
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enum ring_buffer_type {
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RINGBUF_TYPE_PADDING,
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RINGBUF_TYPE_TIME_EXTEND,
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/* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */
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RINGBUF_TYPE_TIME_STAMP,
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RINGBUF_TYPE_DATA,
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};
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unsigned ring_buffer_event_length(struct ring_buffer_event *event);
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void *ring_buffer_event_data(struct ring_buffer_event *event);
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/**
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* ring_buffer_event_time_delta - return the delta timestamp of the event
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* @event: the event to get the delta timestamp of
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*
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* The delta timestamp is the 27 bit timestamp since the last event.
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*/
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static inline unsigned
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ring_buffer_event_time_delta(struct ring_buffer_event *event)
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{
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return event->time_delta;
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}
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/*
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* size is in bytes for each per CPU buffer.
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*/
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struct ring_buffer *
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ring_buffer_alloc(unsigned long size, unsigned flags);
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void ring_buffer_free(struct ring_buffer *buffer);
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int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size);
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struct ring_buffer_event *
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ring_buffer_lock_reserve(struct ring_buffer *buffer,
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unsigned long length,
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unsigned long *flags);
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int ring_buffer_unlock_commit(struct ring_buffer *buffer,
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struct ring_buffer_event *event,
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unsigned long flags);
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int ring_buffer_write(struct ring_buffer *buffer,
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unsigned long length, void *data);
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struct ring_buffer_event *
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ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts);
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struct ring_buffer_event *
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ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts);
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struct ring_buffer_iter *
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ring_buffer_read_start(struct ring_buffer *buffer, int cpu);
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void ring_buffer_read_finish(struct ring_buffer_iter *iter);
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struct ring_buffer_event *
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ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts);
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struct ring_buffer_event *
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ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts);
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void ring_buffer_iter_reset(struct ring_buffer_iter *iter);
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int ring_buffer_iter_empty(struct ring_buffer_iter *iter);
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unsigned long ring_buffer_size(struct ring_buffer *buffer);
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void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu);
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void ring_buffer_reset(struct ring_buffer *buffer);
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int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
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struct ring_buffer *buffer_b, int cpu);
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int ring_buffer_empty(struct ring_buffer *buffer);
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int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu);
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void ring_buffer_record_disable(struct ring_buffer *buffer);
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void ring_buffer_record_enable(struct ring_buffer *buffer);
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void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);
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void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);
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unsigned long ring_buffer_entries(struct ring_buffer *buffer);
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unsigned long ring_buffer_overruns(struct ring_buffer *buffer);
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u64 ring_buffer_time_stamp(int cpu);
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void ring_buffer_normalize_time_stamp(int cpu, u64 *ts);
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enum ring_buffer_flags {
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RB_FL_OVERWRITE = 1 << 0,
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};
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#endif /* _LINUX_RING_BUFFER_H */
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