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SubjectRe: [PATCH] tracing: Update entries counter when removing pages
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On Mon, 2012-06-18 at 12:12 -0700, Vaibhav Nagarnaik wrote:
> When removing pages from the ring buffer, its state is not reset. This
> means that the counters need to be correctly updated to account for the
> pages removed.
>
> Update the entries counter to reflect the removed events from the
> pages just like entries_bytes counter.
>
> Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
> ---
> kernel/trace/ring_buffer.c | 6 +++---
> 1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 96c2dd1..a2bec4c 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -1346,10 +1346,10 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
> * If something was added to this page, it was full
> * since it is not the tail page. So we deduct the
> * bytes consumed in ring buffer from here.
> - * No need to update overruns, since this page is
> - * deleted from ring buffer and its entries are
> - * already accounted for.
> + * No need to update overruns, since updating
> + * 'entries' accounts for that.
> */
> + local_sub(page_entries, &cpu_buffer->entries);

Actually, I think it would be better to increment overrun instead. As
these are lost events, and that is what overrun counts. I just tested it
with: local_add(page_entries, &cpu_buffer->overrun); and it works well.
Showing the lost events.

-- Steve

> local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
> }
>




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