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ring-buffer: Add per_cpu ring buffer control files

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Add a debugfs entry under per_cpu/ folder for each cpu called
buffer_size_kb to control the ring buffer size for each CPU
independently.

If the global file buffer_size_kb is used to set size, the individual
ring buffers will be adjusted to the given size. The buffer_size_kb will
report the common size to maintain backward compatibility.

If the buffer_size_kb file under the per_cpu/ directory is used to
change buffer size for a specific CPU, only the size of the respective
ring buffer is updated. When tracing/buffer_size_kb is read, it reports
'X' to indicate that sizes of per_cpu ring buffers are not equivalent.

Link: http://lkml.kernel.org/r/1328212844-11889-1-git-send-email-vnagarnaik@google.com

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Justin Teravest <teravest@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Vaibhav Nagarnaik 2012-02-02 12:00:41 -08:00 • committed by Steven Rostedt
parent 5a26c8f0cf
commit 438ced1720
4 changed files with 298 additions and 150 deletions
Download patch file Download diff file Expand all files Collapse all files

250
kernel/trace/ring_buffer.c
View file

@ -449,6 +449,7 @@ struct ring_buffer_per_cpu {
raw_spinlock_t reader_lock; /* serialize readers */
arch_spinlock_t lock;
struct lock_class_key lock_key;
unsigned int nr_pages;
struct list_head *pages;
struct buffer_page *head_page; /* read from head */
struct buffer_page *tail_page; /* write to tail */
@ -466,10 +467,12 @@ struct ring_buffer_per_cpu {
unsigned long read_bytes;
u64 write_stamp;
u64 read_stamp;
/* ring buffer pages to update, > 0 to add, < 0 to remove */
int nr_pages_to_update;
struct list_head new_pages; /* new pages to add */
};
struct ring_buffer {
unsigned pages;
unsigned flags;
int cpus;
atomic_t record_disabled;
@ -963,14 +966,10 @@ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
return 0;
}
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
unsigned nr_pages)
static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
{
int i;
struct buffer_page *bpage, *tmp;
LIST_HEAD(pages);
unsigned i;
WARN_ON(!nr_pages);
for (i = 0; i < nr_pages; i++) {
struct page *page;
@ -981,15 +980,13 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
*/
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
GFP_KERNEL | __GFP_NORETRY,
cpu_to_node(cpu_buffer->cpu));
cpu_to_node(cpu));
if (!bpage)
goto free_pages;
rb_check_bpage(cpu_buffer, bpage);
list_add(&bpage->list, pages);
list_add(&bpage->list, &pages);
page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
page = alloc_pages_node(cpu_to_node(cpu),
GFP_KERNEL | __GFP_NORETRY, 0);
if (!page)
goto free_pages;
@ -997,6 +994,27 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
rb_init_page(bpage->page);
}
return 0;
free_pages:
list_for_each_entry_safe(bpage, tmp, pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
return -ENOMEM;
}
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
unsigned nr_pages)
{
LIST_HEAD(pages);
WARN_ON(!nr_pages);
if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
return -ENOMEM;
/*
* The ring buffer page list is a circular list that does not
* start and end with a list head. All page list items point to
@ -1005,20 +1023,15 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
cpu_buffer->pages = pages.next;
list_del(&pages);
cpu_buffer->nr_pages = nr_pages;
rb_check_pages(cpu_buffer);
return 0;
free_pages:
list_for_each_entry_safe(bpage, tmp, &pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
return -ENOMEM;
}
static struct ring_buffer_per_cpu *
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_page *bpage;
@ -1052,7 +1065,7 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
ret = rb_allocate_pages(cpu_buffer, buffer->pages);
ret = rb_allocate_pages(cpu_buffer, nr_pages);
if (ret < 0)
goto fail_free_reader;
@ -1113,7 +1126,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
{
struct ring_buffer *buffer;
int bsize;
int cpu;
int cpu, nr_pages;
/* keep it in its own cache line */
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
@ -1124,14 +1137,14 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
goto fail_free_buffer;
buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
buffer->flags = flags;
buffer->clock = trace_clock_local;
buffer->reader_lock_key = key;
/* need at least two pages */
if (buffer->pages < 2)
buffer->pages = 2;
if (nr_pages < 2)
nr_pages = 2;
/*
* In case of non-hotplug cpu, if the ring-buffer is allocated
@ -1154,7 +1167,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
for_each_buffer_cpu(buffer, cpu) {
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, cpu);
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu])
goto fail_free_buffers;
}
@ -1276,6 +1289,18 @@ out:
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
}
static void update_pages_handler(struct ring_buffer_per_cpu *cpu_buffer)
{
if (cpu_buffer->nr_pages_to_update > 0)
rb_insert_pages(cpu_buffer, &cpu_buffer->new_pages,
cpu_buffer->nr_pages_to_update);
else
rb_remove_pages(cpu_buffer, -cpu_buffer->nr_pages_to_update);
cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
/* reset this value */
cpu_buffer->nr_pages_to_update = 0;
}
/**
* ring_buffer_resize - resize the ring buffer
* @buffer: the buffer to resize.
@ -1285,14 +1310,12 @@ out:
*
* Returns -1 on failure.
*/
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
int cpu_id)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned nr_pages, rm_pages, new_pages;
struct buffer_page *bpage, *tmp;
unsigned long buffer_size;
LIST_HEAD(pages);
int i, cpu;
unsigned nr_pages;
int cpu;
/*
* Always succeed at resizing a non-existent buffer:
@ -1302,15 +1325,11 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
size *= BUF_PAGE_SIZE;
buffer_size = buffer->pages * BUF_PAGE_SIZE;
/* we need a minimum of two pages */
if (size < BUF_PAGE_SIZE * 2)
size = BUF_PAGE_SIZE * 2;
if (size == buffer_size)
return size;
atomic_inc(&buffer->record_disabled);
/* Make sure all writers are done with this buffer. */
@ -1321,68 +1340,56 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
if (size < buffer_size) {
/* easy case, just free pages */
if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
goto out_fail;
rm_pages = buffer->pages - nr_pages;
if (cpu_id == RING_BUFFER_ALL_CPUS) {
/* calculate the pages to update */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
rb_remove_pages(cpu_buffer, rm_pages);
}
goto out;
}
/*
* This is a bit more difficult. We only want to add pages
* when we can allocate enough for all CPUs. We do this
* by allocating all the pages and storing them on a local
* link list. If we succeed in our allocation, then we
* add these pages to the cpu_buffers. Otherwise we just free
* them all and return -ENOMEM;
*/
if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
goto out_fail;
cpu_buffer->nr_pages_to_update = nr_pages -
cpu_buffer->nr_pages;
new_pages = nr_pages - buffer->pages;
for_each_buffer_cpu(buffer, cpu) {
for (i = 0; i < new_pages; i++) {
struct page *page;
/*
* __GFP_NORETRY flag makes sure that the allocation
* fails gracefully without invoking oom-killer and
* the system is not destabilized.
* nothing more to do for removing pages or no update
*/
bpage = kzalloc_node(ALIGN(sizeof(*bpage),
cache_line_size()),
GFP_KERNEL | __GFP_NORETRY,
cpu_to_node(cpu));
if (!bpage)
goto free_pages;
list_add(&bpage->list, &pages);
page = alloc_pages_node(cpu_to_node(cpu),
GFP_KERNEL | __GFP_NORETRY, 0);
if (!page)
goto free_pages;
bpage->page = page_address(page);
rb_init_page(bpage->page);
if (cpu_buffer->nr_pages_to_update <= 0)
continue;
/*
* to add pages, make sure all new pages can be
* allocated without receiving ENOMEM
*/
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
&cpu_buffer->new_pages, cpu))
/* not enough memory for new pages */
goto no_mem;
}
}
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
rb_insert_pages(cpu_buffer, &pages, new_pages);
}
/* wait for all the updates to complete */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
if (cpu_buffer->nr_pages_to_update) {
update_pages_handler(cpu_buffer);
}
}
} else {
cpu_buffer = buffer->buffers[cpu_id];
if (nr_pages == cpu_buffer->nr_pages)
goto out;
if (RB_WARN_ON(buffer, !list_empty(&pages)))
goto out_fail;
cpu_buffer->nr_pages_to_update = nr_pages -
cpu_buffer->nr_pages;
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (cpu_buffer->nr_pages_to_update > 0 &&
__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
&cpu_buffer->new_pages, cpu_id))
goto no_mem;
update_pages_handler(cpu_buffer);
}
out:
buffer->pages = nr_pages;
put_online_cpus();
mutex_unlock(&buffer->mutex);
@ -1390,25 +1397,24 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
return size;
free_pages:
list_for_each_entry_safe(bpage, tmp, &pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
no_mem:
for_each_buffer_cpu(buffer, cpu) {
struct buffer_page *bpage, *tmp;
cpu_buffer = buffer->buffers[cpu];
/* reset this number regardless */
cpu_buffer->nr_pages_to_update = 0;
if (list_empty(&cpu_buffer->new_pages))
continue;
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
}
put_online_cpus();
mutex_unlock(&buffer->mutex);
atomic_dec(&buffer->record_disabled);
return -ENOMEM;
/*
* Something went totally wrong, and we are too paranoid
* to even clean up the mess.
*/
out_fail:
put_online_cpus();
mutex_unlock(&buffer->mutex);
atomic_dec(&buffer->record_disabled);
return -1;
}
EXPORT_SYMBOL_GPL(ring_buffer_resize);
@ -1510,7 +1516,7 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
* assign the commit to the tail.
*/
again:
max_count = cpu_buffer->buffer->pages * 100;
max_count = cpu_buffer->nr_pages * 100;
while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
if (RB_WARN_ON(cpu_buffer, !(--max_count)))
@ -3588,9 +3594,18 @@ EXPORT_SYMBOL_GPL(ring_buffer_read);
* ring_buffer_size - return the size of the ring buffer (in bytes)
* @buffer: The ring buffer.
*/
unsigned long ring_buffer_size(struct ring_buffer *buffer)
unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
{
return BUF_PAGE_SIZE * buffer->pages;
/*
* Earlier, this method returned
* BUF_PAGE_SIZE * buffer->nr_pages
* Since the nr_pages field is now removed, we have converted this to
* return the per cpu buffer value.
*/
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
}
EXPORT_SYMBOL_GPL(ring_buffer_size);
@ -3765,8 +3780,11 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
!cpumask_test_cpu(cpu, buffer_b->cpumask))
goto out;
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
/* At least make sure the two buffers are somewhat the same */
if (buffer_a->pages != buffer_b->pages)
if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
goto out;
ret = -EAGAIN;
@ -3780,9 +3798,6 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
if (atomic_read(&buffer_b->record_disabled))
goto out;
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
if (atomic_read(&cpu_buffer_a->record_disabled))
goto out;
@ -4071,6 +4086,8 @@ static int rb_cpu_notify(struct notifier_block *self,
struct ring_buffer *buffer =
container_of(self, struct ring_buffer, cpu_notify);
long cpu = (long)hcpu;
int cpu_i, nr_pages_same;
unsigned int nr_pages;
switch (action) {
case CPU_UP_PREPARE:
@ -4078,8 +4095,23 @@ static int rb_cpu_notify(struct notifier_block *self,
if (cpumask_test_cpu(cpu, buffer->cpumask))
return NOTIFY_OK;
nr_pages = 0;
nr_pages_same = 1;
/* check if all cpu sizes are same */
for_each_buffer_cpu(buffer, cpu_i) {
/* fill in the size from first enabled cpu */
if (nr_pages == 0)
nr_pages = buffer->buffers[cpu_i]->nr_pages;
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
nr_pages_same = 0;
break;
}
}
/* allocate minimum pages, user can later expand it */
if (!nr_pages_same)
nr_pages = 2;
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, cpu);
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu]) {
WARN(1, "failed to allocate ring buffer on CPU %ld\n",
cpu);