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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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