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ring-buffer: Add page statistics to the meta-page

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Add two fields pages_touched and pages_lost to the ring-buffer
meta-page. Those fields are useful to get the number of used pages in
the ring-buffer.

Link: https://patch.msgid.link/20260309162516.2623589-2-vdonnefort@google.com
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Vincent Donnefort
2026-03-09 16:24:47 +00:00
committed by Steven Rostedt (Google)
parent 1f318b96cc
commit 7d776a3627
2 changed files with 6 additions and 4 deletions
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8
include/uapi/linux/trace_mmap.h
View File

@@ -17,8 +17,8 @@
* @entries: Number of entries in the ring-buffer.
* @overrun: Number of entries lost in the ring-buffer.
* @read: Number of entries that have been read.
* @Reserved1: Internal use only.
* @Reserved2: Internal use only.
* @pages_lost: Number of pages overwritten by the writer.
* @pages_touched: Number of pages written by the writer.
*/
struct trace_buffer_meta {
__u32 meta_page_size;
@@ -39,8 +39,8 @@ struct trace_buffer_meta {
__u64 overrun;
__u64 read;
__u64 Reserved1;
__u64 Reserved2;
__u64 pages_lost;
__u64 pages_touched;
};
#define TRACE_MMAP_IOCTL_GET_READER _IO('R', 0x20)

2
kernel/trace/ring_buffer.c
View File

@@ -6154,6 +6154,8 @@ static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
meta->entries = local_read(&cpu_buffer->entries);
meta->overrun = local_read(&cpu_buffer->overrun);
meta->read = cpu_buffer->read;
meta->pages_lost = local_read(&cpu_buffer->pages_lost);
meta->pages_touched = local_read(&cpu_buffer->pages_touched);
/* Some archs do not have data cache coherency between kernel and user-space */
flush_kernel_vmap_range(cpu_buffer->meta_page, PAGE_SIZE);