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Subject[RFC PATCH 16/20] Ring buffer library - client sample
Example ring buffer library client.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
samples/Kconfig | 8
samples/Makefile | 2
samples/ring_buffer_user/Makefile | 4
samples/ring_buffer_user/ring_buffer_template_user.c | 273 +++++++++++++++++++
samples/ring_buffer_user/ring_buffer_template_user.h | 100 ++++++
5 files changed, 386 insertions(+), 1 deletion(-)
Index: linux.trees.git/samples/Makefile
===================================================================
--- linux.trees.git.orig/samples/Makefile 2010-08-17 16:28:26.000000000 -0400
+++ linux.trees.git/samples/Makefile 2010-08-17 17:02:58.000000000 -0400
@@ -1,4 +1,4 @@
# Makefile for Linux samples code

obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ tracepoints/ trace_events/ \
- hw_breakpoint/ kfifo/
+ hw_breakpoint/ kfifo/ ring_buffer_user/
Index: linux.trees.git/samples/ring_buffer_user/ring_buffer_template_user.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux.trees.git/samples/ring_buffer_user/ring_buffer_template_user.c 2010-08-17 17:02:23.000000000 -0400
@@ -0,0 +1,273 @@
+/*
+ * ring_buffer_template_user.c
+ *
+ * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Ring buffer template instance code example.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <linux/module.h>
+#include <linux/debugfs.h>
+
+#include "ring_buffer_template_user.h"
+
+struct ring_buffer_priv {
+ struct dentry *dentry;
+};
+
+struct channel_priv {
+ struct ring_buffer_priv *buf;
+};
+
+static struct channel *chan;
+static struct channel_priv channel_priv;
+static const struct ring_buffer_config client_config;
+
+/* Client callbacks */
+
+static u64 client_ring_buffer_clock_read(struct channel *chan)
+{
+ return ring_buffer_clock_read(chan);
+}
+
+size_t client_record_header_size(const struct ring_buffer_config *config,
+ struct channel *chan, size_t offset,
+ size_t data_size,
+ size_t *pre_header_padding,
+ unsigned int rflags,
+ struct ring_buffer_ctx *ctx)
+{
+ return record_header_size(config, chan, offset, data_size,
+ pre_header_padding, rflags, ctx);
+}
+
+/**
+ * ring_buffer_sb_header_size - called on buffer-switch to a new sub-buffer
+ *
+ * Return header size without padding after the structure. Don't use packed
+ * structure because gcc generates inefficient code on some architectures
+ * (powerpc, mips..)
+ */
+static size_t client_subbuffer_header_size(void)
+{
+ return offsetof(struct subbuffer_header, header_end);
+}
+
+/**
+ * ring_buffer_write_trace_header - Write trace header
+ * @trace: Trace information
+ * @header: Memory address where the information must be written to
+ */
+static inline
+void write_trace_header(void *priv, struct subbuffer_header *header)
+{
+ header->magic_number = 0x12345678;
+ header->alignment = ring_buffer_get_alignment(&client_config);
+ /* ... */
+}
+
+static void client_buffer_begin(struct ring_buffer *buf, u64 tsc,
+ unsigned int subbuf_idx)
+{
+ struct channel *chan = buf->backend.chan;
+ struct subbuffer_header *header =
+ (struct subbuffer_header *)
+ ring_buffer_offset_address(&buf->backend,
+ subbuf_idx * chan->backend.subbuf_size);
+
+ header->cycle_count_begin = tsc;
+ header->data_size = 0xFFFFFFFF; /* for debugging */
+ write_trace_header(chan->backend.priv, header);
+}
+
+/*
+ * offset is assumed to never be 0 here : never deliver a completely empty
+ * subbuffer. data_size is between 1 and subbuf_size.
+ */
+static void client_buffer_end(struct ring_buffer *buf, u64 tsc,
+ unsigned int subbuf_idx, unsigned long data_size)
+{
+ struct channel *chan = buf->backend.chan;
+ struct subbuffer_header *header =
+ (struct subbuffer_header *)
+ ring_buffer_offset_address(&buf->backend,
+ subbuf_idx * chan->backend.subbuf_size);
+ unsigned long records_lost = 0;
+
+ header->data_size = data_size;
+ header->subbuf_size = PAGE_ALIGN(data_size);
+ header->cycle_count_end = tsc;
+ records_lost += ring_buffer_get_records_lost_full(&client_config, buf);
+ records_lost += ring_buffer_get_records_lost_wrap(&client_config, buf);
+ records_lost += ring_buffer_get_records_lost_big(&client_config, buf);
+ header->records_lost = records_lost;
+}
+
+static int client_buffer_create(struct ring_buffer *buf, void *priv,
+ int cpu, const char *name)
+{
+ struct channel_priv *chan_priv = priv;
+ struct ring_buffer_priv *buf_priv;
+ char *tmpname;
+ int ret = 0;
+
+ if (client_config.alloc == RING_BUFFER_ALLOC_PER_CPU)
+ buf_priv = per_cpu_ptr(chan_priv->buf, cpu);
+ else
+ buf_priv = chan_priv->buf;
+
+ tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
+ if (!tmpname) {
+ ret = -ENOMEM;
+ goto end;
+ }
+
+ snprintf(tmpname, NAME_MAX, "%s%s_%d",
+ (client_config.mode == RING_BUFFER_OVERWRITE) ? "flight-" : "",
+ name, cpu);
+
+ buf_priv->dentry = debugfs_create_file(tmpname, S_IRUSR, NULL, buf,
+ &ring_buffer_file_operations);
+ if (!buf_priv->dentry) {
+ ret = -ENOMEM;
+ goto free_name;
+ }
+free_name:
+ kfree(tmpname);
+end:
+ return ret;
+}
+
+static void client_buffer_finalize(struct ring_buffer *buf, void *priv, int cpu)
+{
+ struct channel_priv *chan_priv = priv;
+ struct ring_buffer_priv *buf_priv;
+
+ if (client_config.alloc == RING_BUFFER_ALLOC_PER_CPU)
+ buf_priv = per_cpu_ptr(chan_priv->buf, cpu);
+ else
+ buf_priv = chan_priv->buf;
+
+ debugfs_remove(buf_priv->dentry);
+}
+
+static const struct ring_buffer_config client_config = {
+ .cb.ring_buffer_clock_read = client_ring_buffer_clock_read,
+ .cb.record_header_size = client_record_header_size,
+ .cb.subbuffer_header_size = client_subbuffer_header_size,
+ .cb.buffer_begin = client_buffer_begin,
+ .cb.buffer_end = client_buffer_end,
+ .cb.buffer_create = client_buffer_create,
+ .cb.buffer_finalize = client_buffer_finalize,
+
+ .tsc_bits = 64,
+ .alloc = RING_BUFFER_ALLOC_PER_CPU,
+ .sync = RING_BUFFER_SYNC_PER_CPU,
+ .mode = RING_BUFFER_OVERWRITE,
+ .align = RING_BUFFER_NATURAL,
+ .backend = RING_BUFFER_PAGE,
+ .output = RING_BUFFER_SPLICE,
+ .oops = RING_BUFFER_OOPS_CONSISTENCY,
+ .ipi = RING_BUFFER_IPI_BARRIER,
+ .wakeup = RING_BUFFER_WAKEUP_BY_TIMER,
+};
+
+static void write_event_header(const struct ring_buffer_config *config,
+ struct ring_buffer_ctx *ctx)
+{
+ ring_buffer_write(config, ctx, &ctx->tsc, sizeof(ctx->tsc));
+}
+
+static noinline void trace_event(unsigned long data1, short data2)
+{
+ struct ring_buffer_ctx ctx;
+ int ret, cpu;
+
+ cpu = ring_buffer_get_cpu(&client_config);
+ if (cpu < 0)
+ return;
+ ring_buffer_ctx_init(&ctx, chan, &channel_priv,
+ sizeof(struct payload),
+ sizeof(unsigned long),
+ cpu);
+
+ ret = ring_buffer_reserve(&client_config, &ctx);
+ if (ret)
+ goto put;
+
+ write_event_header(&client_config, &ctx);
+
+ ring_buffer_align_ctx(&client_config, &ctx, sizeof(data1));
+ ring_buffer_write(&client_config, &ctx, &data1, sizeof(data1));
+ ring_buffer_align_ctx(&client_config, &ctx, sizeof(data2));
+ ring_buffer_write(&client_config, &ctx, &data2, sizeof(data2));
+
+ ring_buffer_commit(&client_config, &ctx);
+
+put:
+ ring_buffer_put_cpu(&client_config);
+}
+
+static noinline void use_ring_buffer(void)
+{
+ unsigned long i;
+
+ for (i = 0; i < 1000000; i++)
+ trace_event(i, (short)i);
+}
+
+static int __init ring_buffer_client_init(void)
+{
+ int ret;
+
+ printk(KERN_DEBUG "Ring buffer client init begin\n");
+
+ if (client_config.alloc == RING_BUFFER_ALLOC_PER_CPU)
+ channel_priv.buf = alloc_percpu(struct ring_buffer_priv);
+ else
+ channel_priv.buf = kzalloc(sizeof(struct ring_buffer_priv),
+ GFP_KERNEL);
+ if (!channel_priv.buf)
+ return -ENOMEM;
+
+ chan = channel_create(&client_config, "sample", &channel_priv, NULL,
+ 1048576, 2,
+ 100000, 1000);
+ if (!chan) {
+ ret = -EINVAL;
+ goto error_create;
+ }
+
+ printk(KERN_DEBUG "Ring buffer client init end\n");
+
+ use_ring_buffer();
+
+ return 0;
+
+error_create:
+ if (client_config.alloc == RING_BUFFER_ALLOC_PER_CPU)
+ free_percpu(channel_priv.buf);
+ else
+ kfree(channel_priv.buf);
+ return ret;
+}
+
+static void __exit ring_buffer_client_exit(void)
+{
+ printk(KERN_DEBUG "Ring buffer client exit begin\n");
+ channel_destroy(chan);
+ if (client_config.alloc == RING_BUFFER_ALLOC_PER_CPU)
+ free_percpu(channel_priv.buf);
+ else
+ kfree(channel_priv.buf);
+ printk(KERN_DEBUG "Ring buffer client exit end\n");
+}
+
+module_init(ring_buffer_client_init);
+module_exit(ring_buffer_client_exit);
+
+MODULE_LICENSE("GPL and additional rights");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Ring Buffer Client Template");
Index: linux.trees.git/samples/ring_buffer_user/ring_buffer_template_user.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux.trees.git/samples/ring_buffer_user/ring_buffer_template_user.h 2010-08-17 17:02:23.000000000 -0400
@@ -0,0 +1,100 @@
+#ifndef _RING_BUFFER_TEMPLATE_USER_H
+#define _RING_BUFFER_TEMPLATE_USER_H
+
+/*
+ * ring_buffer_template_user.h
+ *
+ * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Ring buffer template instance code example.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <linux/types.h>
+#include <linux/trace_clock.h>
+
+/* Align data on its natural alignment */
+#define RING_BUFFER_ALIGN
+
+#include <linux/ringbuffer/config.h>
+
+struct subbuffer_header {
+ uint64_t cycle_count_begin; /* Cycle count at subbuffer start */
+ uint64_t cycle_count_end; /* Cycle count at subbuffer end */
+ uint32_t magic_number; /*
+ * Trace magic number.
+ * contains endianness information.
+ */
+ uint8_t major_version;
+ uint8_t minor_version;
+ uint8_t arch_size; /* Architecture pointer size */
+ uint8_t alignment; /* ring buffer data alignment */
+ uint64_t start_time_sec; /* NTP-corrected start time */
+ uint64_t start_time_usec;
+ uint64_t start_freq; /*
+ * Frequency at trace start,
+ * used all along the trace.
+ */
+ uint32_t freq_scale; /* Frequency scaling (divisor) */
+ uint32_t data_size; /* Size of data in subbuffer */
+ uint32_t subbuf_size; /* Subbuffer size (include padding) */
+ uint32_t records_lost; /*
+ * Records lost in this subbuffer since
+ * the beginning of the trace.
+ * (may overflow)
+ */
+ uint8_t header_end[0]; /* End of header */
+};
+
+struct event_header {
+ u64 tsc;
+};
+
+struct payload {
+ unsigned long field1;
+ short field2;
+} RING_BUFFER_ALIGN_ATTR;
+
+/*
+ * Using the trace_clock_global() as an example.
+ */
+static inline notrace u64 ring_buffer_clock_read(struct channel *chan)
+{
+ return trace_clock_global();
+}
+
+/*
+ * record_header_size - Calculate the header size and padding necessary.
+ * @config: ring buffer instance configuration
+ * @chan: channel
+ * @offset: offset in the write buffer
+ * @data_size: size of the payload
+ * @pre_header_padding: padding to add before the header (output)
+ * @rflags: reservation flags
+ * @ctx: reservation context
+ *
+ * Returns the event header size (including padding).
+ */
+static inline notrace
+unsigned char record_header_size(const struct ring_buffer_config *config,
+ struct channel *chan, size_t offset,
+ size_t data_size, size_t *pre_header_padding,
+ unsigned int rflags,
+ struct ring_buffer_ctx *ctx)
+{
+ size_t orig_offset = offset;
+ size_t padding;
+
+ padding = ring_buffer_align(config, offset,
+ sizeof(struct event_header));
+ offset += padding;
+ offset += sizeof(struct event_header);
+
+ *pre_header_padding = padding;
+ return offset - orig_offset;
+}
+
+#include <linux/ringbuffer/api.h>
+
+#endif /* _RING_BUFFER_TEMPLATE_USER_H */
Index: linux.trees.git/samples/Kconfig
===================================================================
--- linux.trees.git.orig/samples/Kconfig 2010-08-17 17:02:18.000000000 -0400
+++ linux.trees.git/samples/Kconfig 2010-08-17 17:02:43.000000000 -0400
@@ -54,4 +54,12 @@ config SAMPLE_KFIFO

If in doubt, say "N" here.

+config SAMPLE_LIB_RING_BUFFER_TEMPLATE
+ tristate "Build ring buffer template user -- loadable modules only"
+ default m
+ depends on LIB_RING_BUFFER
+ select TRACE_CLOCK_STANDALONE
+ help
+ This builds the ring buffer template user.
+
endif # SAMPLES
Index: linux.trees.git/samples/ring_buffer_user/Makefile
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux.trees.git/samples/ring_buffer_user/Makefile 2010-08-17 17:02:23.000000000 -0400
@@ -0,0 +1,4 @@
+# builds the ring buffer template user example kernel modules;
+# then to use one (as root): insmod <module_name.ko>
+
+obj-$(CONFIG_SAMPLE_LIB_RING_BUFFER_TEMPLATE) += ring_buffer_template_user.o


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