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Date: Tue, 2 Dec 2008 16:55:09 -0800
From: Jiaying Zhang <jiayingz@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Steven Rostedt <srostedt@...hat.com>,
Martin Bligh <mbligh@...gle.com>,
Michael Rubin <mrubin@...gle.com>,
Michael Davidson <md@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [RFC PATCH 1/3] adding mmap support to the unified trace buffer
Refer to the previous email
"[RFC PATCH 0/3] A couple of feature requests to the unified trace buffer".
Add the mmap support to the unified trace buffer. The patch includes an
API that maps a page offset to a physical page in a trace buffer, APIs
that export the offset of the current produced/consumed data, and an
API to advance the consumed data pointer.
Index: linux-2.6.26/include/linux/ring_buffer.h
===================================================================
--- linux-2.6.26.orig/include/linux/ring_buffer.h 2008-12-01
14:46:11.000000000 -0800
+++ linux-2.6.26/include/linux/ring_buffer.h 2008-12-01
14:46:30.000000000 -0800
@@ -5,6 +5,7 @@
#include <linux/seq_file.h>
struct ring_buffer;
+struct ring_buffer_per_cpu;
struct ring_buffer_iter;
/*
@@ -108,6 +109,7 @@
int ring_buffer_empty(struct ring_buffer *buffer);
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu);
+int ring_buffer_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer);
void ring_buffer_record_disable(struct ring_buffer *buffer);
void ring_buffer_record_enable(struct ring_buffer *buffer);
@@ -124,4 +126,12 @@
RB_FL_OVERWRITE = 1 << 0,
};
+struct ring_buffer_per_cpu *ring_buffer_cpu(struct ring_buffer *buffer,
+ int cpu);
+struct page * ring_buffer_get_page(struct ring_buffer_per_cpu *cpu_buffer,
+ pgoff_t pgoff);
+void ring_buffer_advance_reader(struct ring_buffer_per_cpu *cpu_buffer,
+ int count_in);
+u32 ring_buffer_get_produced(struct ring_buffer_per_cpu *cpu_buffer);
+u32 ring_buffer_get_consumed(struct ring_buffer_per_cpu *cpu_buffer);
#endif /* _LINUX_RING_BUFFER_H */
Index: linux-2.6.26/kernel/ktrace/ring_buffer.c
===================================================================
--- linux-2.6.26.orig/kernel/ktrace/ring_buffer.c 2008-12-01
14:46:11.000000000 -0800
+++ linux-2.6.26/kernel/ktrace/ring_buffer.c 2008-12-01
16:03:01.000000000 -0800
@@ -131,7 +131,6 @@
{
if (bpage->page)
free_page((unsigned long)bpage->page);
- kfree(bpage);
}
/*
@@ -155,6 +154,7 @@
spinlock_t lock;
struct lock_class_key lock_key;
struct list_head pages;
+ struct buffer_page *page_array;
struct buffer_page *head_page; /* read from head */
struct buffer_page *tail_page; /* write to tail */
struct buffer_page *commit_page; /* commited pages */
@@ -186,6 +186,11 @@
u64 read_stamp;
};
+struct ring_buffer_per_cpu *ring_buffer_cpu(struct ring_buffer
*buffer, int cpu)
+{
+ return buffer->buffers[cpu];
+}
+
#define RB_WARN_ON(buffer, cond) \
do { \
if (unlikely(cond)) { \
@@ -238,25 +243,26 @@
return 0;
}
+#define BP_HEADER_SIZE ALIGN(sizeof(struct buffer_page), cache_line_size())
+
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
unsigned nr_pages)
{
struct list_head *head = &cpu_buffer->pages;
- struct buffer_page *page, *tmp;
+ struct buffer_page *page;
+ void *array;
unsigned long addr;
LIST_HEAD(pages);
unsigned i;
+ array = cpu_buffer->page_array;
for (i = 0; i < nr_pages; i++) {
- page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
- GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
- if (!page)
- goto free_pages;
- list_add(&page->list, &pages);
+ page = (struct buffer_page *) (array + i * BP_HEADER_SIZE);
+ list_add_tail(&page->list, &pages);
addr = __get_free_page(GFP_KERNEL);
if (!addr)
- goto free_pages;
+ return -ENOMEM;
page->page = (void *)addr;
}
@@ -265,13 +271,6 @@
rb_check_pages(cpu_buffer);
return 0;
-
- free_pages:
- list_for_each_entry_safe(page, tmp, &pages, list) {
- list_del_init(&page->list);
- free_buffer_page(page);
- }
- return -ENOMEM;
}
static struct ring_buffer_per_cpu *
@@ -292,22 +291,23 @@
spin_lock_init(&cpu_buffer->lock);
INIT_LIST_HEAD(&cpu_buffer->pages);
- page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
- GFP_KERNEL, cpu_to_node(cpu));
- if (!page)
+ cpu_buffer->page_array = kzalloc_node(BP_HEADER_SIZE * buffer->pages,
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!cpu_buffer->page_array)
goto fail_free_buffer;
+ page = (struct buffer_page *) ((void *) cpu_buffer->page_array +
+ BP_HEADER_SIZE * (buffer->pages -1));
cpu_buffer->reader_page = page;
addr = __get_free_page(GFP_KERNEL);
if (!addr)
- goto fail_free_reader;
+ goto fail_free_array;
page->page = (void *)addr;
-
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
- ret = rb_allocate_pages(cpu_buffer, buffer->pages);
+ ret = rb_allocate_pages(cpu_buffer, buffer->pages - 1);
if (ret < 0)
- goto fail_free_reader;
+ goto fail_free_array;
cpu_buffer->head_page
= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
@@ -315,8 +315,8 @@
return cpu_buffer;
- fail_free_reader:
- free_buffer_page(cpu_buffer->reader_page);
+ fail_free_array:
+ kfree(cpu_buffer->page_array);
fail_free_buffer:
kfree(cpu_buffer);
@@ -335,6 +335,7 @@
list_del_init(&page->list);
free_buffer_page(page);
}
+ kfree(cpu_buffer->page_array);
kfree(cpu_buffer);
}
@@ -439,7 +440,7 @@
for (i = 0; i < nr_pages; i++) {
BUG_ON(list_empty(&cpu_buffer->pages));
- p = cpu_buffer->pages.next;
+ p = cpu_buffer->pages.prev;
page = list_entry(p, struct buffer_page, list);
list_del_init(&page->list);
free_buffer_page(page);
@@ -497,7 +498,7 @@
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned nr_pages, rm_pages, new_pages;
- struct buffer_page *page, *tmp;
+ struct buffer_page *page, *array;
unsigned long buffer_size;
unsigned long addr;
LIST_HEAD(pages);
@@ -544,23 +545,23 @@
new_pages = nr_pages - buffer->pages;
for_each_buffer_cpu(buffer, cpu) {
+ cpu_buffer = buffer->buffers[cpu];
+ array = kzalloc_node(BP_HEADER_SIZE * nr_pages,
+ GFP_KERNEL, cpu_to_node(cpu));
+ memcpy(array, cpu_buffer->page_array,
+ BP_HEADER_SIZE * buffer->pages);
for (i = 0; i < new_pages; i++) {
- page = kzalloc_node(ALIGN(sizeof(*page),
- cache_line_size()),
- GFP_KERNEL, cpu_to_node(cpu));
- if (!page)
- goto free_pages;
- list_add(&page->list, &pages);
+ page = (struct buffer_page *) ((void *) array +
+ (buffer->pages + i) * BP_HEADER_SIZE);
addr = __get_free_page(GFP_KERNEL);
if (!addr)
- goto free_pages;
+ return -ENOMEM;
page->page = (void *)addr;
+ list_add_tail(&page->list, &pages);
}
- }
-
- for_each_buffer_cpu(buffer, cpu) {
- cpu_buffer = buffer->buffers[cpu];
rb_insert_pages(cpu_buffer, &pages, new_pages);
+ kfree(cpu_buffer->page_array);
+ cpu_buffer->page_array = array;
}
BUG_ON(!list_empty(&pages));
@@ -570,13 +571,6 @@
mutex_unlock(&buffer->mutex);
return size;
-
- free_pages:
- list_for_each_entry_safe(page, tmp, &pages, list) {
- list_del_init(&page->list);
- free_buffer_page(page);
- }
- return -ENOMEM;
}
static inline int rb_null_event(struct ring_buffer_event *event)
@@ -1299,6 +1293,11 @@
head->read == rb_page_commit(commit)));
}
+int ring_buffer_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ return rb_per_cpu_empty(cpu_buffer);
+}
+
/**
* ring_buffer_record_disable - stop all writes into the buffer
* @buffer: The ring buffer to stop writes to.
@@ -1638,6 +1637,58 @@
cpu_buffer->reader_page->read += length;
}
+u32 ring_buffer_get_produced(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *reader;
+ unsigned pgoff;
+
+ reader = rb_get_reader_page(cpu_buffer);
+ if (!reader)
+ return 0;
+ pgoff = ((void *) reader - (void *) cpu_buffer->page_array) /
+ BP_HEADER_SIZE;
+ return pgoff * BUF_PAGE_SIZE + rb_page_commit(reader);
+}
+
+u32 ring_buffer_get_consumed(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *reader;
+ unsigned pgoff;
+
+ reader = rb_get_reader_page(cpu_buffer);
+ if (!reader)
+ return 0;
+ pgoff = ((void *) reader - (void *) cpu_buffer->page_array) /
+ BP_HEADER_SIZE;
+ return pgoff * BUF_PAGE_SIZE + reader->read;
+}
+
+void ring_buffer_advance_reader(struct ring_buffer_per_cpu *cpu_buffer,
+ int count)
+{
+ unsigned long flags;
+ struct buffer_page *reader;
+
+ spin_lock_irqsave(&cpu_buffer->lock, flags);
+ reader = cpu_buffer->reader_page;
+ reader->read += count;
+ spin_unlock_irqrestore(&cpu_buffer->lock, flags);
+}
+
+struct page * ring_buffer_get_page(struct ring_buffer_per_cpu *cpu_buffer,
+ pgoff_t pgoff)
+{
+ struct page *page;
+ struct buffer_page *bpage;
+
+ bpage = (struct buffer_page *) ((void *) cpu_buffer->page_array +
+ pgoff * BP_HEADER_SIZE);
+ page = virt_to_page(bpage->page);
+ if (!page)
+ printk("error: fail to vmalloc page\n");
+ return page;
+}
+
static void rb_advance_iter(struct ring_buffer_iter *iter)
{
struct ring_buffer *buffer;
--
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