ring-buffer: Add per_cpu ring buffer control files
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>
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index cf8d11e..2d5eb33 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -449,6 +449,7 @@
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 @@
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 @@
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 @@
*/
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 @@
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 @@
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 @@
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 *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 @@
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 @@
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 @@
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 @@
*
* 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 @@
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 @@
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 @@
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 @@
* 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 @@
* 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 @@
!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 @@
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 @@
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 @@
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);