On Mon, Sep 07, 2026 at 11:41:46PM +0900, Masami Hiramatsu wrote: > On Mon, 7 Sep 2026 10:42:38 +0100 > Vincent Donnefort <[email protected]> wrote: > > > Since commit 8a5f63637890 ("ring-buffer: Fix subbuf resize race with ring > > buffer readers"), "capacity" refers to the memory available for events > > (excluding subbuffer headers) while "size" refers to the raw allocation. > > ring_buffer_size() actually calculates this event capacity. Rename it to > > ring_buffer_capacity() to align with this convention. > > I think this is OK, but I have a question. > > [...] > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > index 8658cad53cb5..f0251788ec75 100644 > > --- a/kernel/trace/trace.c > > +++ b/kernel/trace/trace.c > > @@ -4712,9 +4712,9 @@ void trace_set_buffer_entries(struct array_buffer > > *buf, unsigned long val) > > static void update_buffer_entries(struct array_buffer *buf, int cpu) > > { > > if (cpu == RING_BUFFER_ALL_CPUS) { > > - trace_set_buffer_entries(buf, ring_buffer_size(buf->buffer, 0)); > > + trace_set_buffer_entries(buf, ring_buffer_capacity(buf->buffer, > > 0)); > > } else { > > - per_cpu_ptr(buf->data, cpu)->entries = > > ring_buffer_size(buf->buffer, cpu); > > + per_cpu_ptr(buf->data, cpu)->entries = > > ring_buffer_capacity(buf->buffer, cpu); > > nit: Don't we need to re-word this "entries" with "capacity" too? > > Actually, this "entries" is a bit odd because > > - ring_buffer_entries() returns the number of events. > - trace_set_buffer_entries() sets the buffer capacity in bytes. > > It seems we call it as "entries" historical reason, but now it becomes the > source of confusion. Maybe we should change it too. (but in the separate > patch) > > Thanks,
Yes, I believe you're right, this "entries" here seems only used for buffer_size_kb, buffer_total_size_kb and resize_buffer_duplicate_size() so we can probably use "capacity" there too, it'll be less confusing than "entries". I'll respin a v2 with that additional patch. (and a fix to the typo) -- Vincent > > > } > > } > > > > @@ -8476,7 +8476,7 @@ int allocate_trace_buffer(struct trace_array *tr, > > struct array_buffer *buf, int > > > > /* Allocate the first page for all buffers */ > > trace_set_buffer_entries(&tr->array_buffer, > > - ring_buffer_size(tr->array_buffer.buffer, 0)); > > + ring_buffer_capacity(tr->array_buffer.buffer, > > 0)); > > > > return 0; > > } > > > > base-commit: df2908090cda368b01ff43709f51890076c56157 > > -- > > 2.55.0.979.g7e5102b832-goog > > > > > -- > Masami Hiramatsu (Google) <[email protected]>
