[PATCH v8 01/28] ring-buffer: Add page statistics to the meta-page
From: Vincent Donnefort <hidden>
Date: 2025-11-07 09:38:50
Also in:
kvmarm, linux-trace-kernel, lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
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. Signed-off-by: Vincent Donnefort <redacted>
diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mmap.h
index c102ef35d11e..e8185889a1c8 100644
--- a/include/uapi/linux/trace_mmap.h
+++ b/include/uapi/linux/trace_mmap.h@@ -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)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 1244d2c5c384..6e912527e44f 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c@@ -6113,6 +6113,8 @@ 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);
--
2.51.2.1041.gc1ab5b90ca-goog