From: "Steven Rostedt (Google)" <rost...@goodmis.org> The trace_seq buffer is used to print out entire events. It's typically set to PAGE_SIZE * 2 as there's some events that can be quite large.
As a side effect, writes to trace_marker is limited by both the size of the trace_seq buffer as well as the ring buffer's sub-buffer size (which is a power of PAGE_SIZE). By limiting the trace_seq size, it also limits the size of the largest string written to trace_marker. trace_seq does not need to be dependent on PAGE_SIZE like the ring buffer sub-buffers need to be. Hard code it to 8K which is PAGE_SIZE * 2 on most architectures. This will also limit the size of trace_marker on those architectures with greater than 4K PAGE_SIZE. Link: https://lore.kernel.org/all/20240302111244.3a167...@gandalf.local.home/ Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org> --- include/linux/trace_seq.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h index 9ec229dfddaa..1ef95c0287f0 100644 --- a/include/linux/trace_seq.h +++ b/include/linux/trace_seq.h @@ -9,9 +9,15 @@ /* * Trace sequences are used to allow a function to call several other functions * to create a string of data to use. + * + * Have the trace seq to be 8K which is typically PAGE_SIZE * 2 on + * most architectures. The TRACE_SEQ_BUFFER_SIZE (which is + * TRACE_SEQ_SIZE minus the other fields of trace_seq), is the + * max size the output of a trace event may be. */ -#define TRACE_SEQ_BUFFER_SIZE (PAGE_SIZE * 2 - \ +#define TRACE_SEQ_SIZE 8192 +#define TRACE_SEQ_BUFFER_SIZE (TRACE_SEQ_SIZE - \ (sizeof(struct seq_buf) + sizeof(size_t) + sizeof(int))) struct trace_seq { -- 2.43.0
