Re: [PATCHv3] perf: Fix vmalloc ring buffer free function

From: Peter Zijlstra
Date: Tue Mar 12 2013 - 11:26:41 EST


On Tue, 2013-03-12 at 14:52 +0100, Jiri Olsa wrote:
> > @@ -373,7 +373,7 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
> > rb->user_page = all_buf;
> > rb->data_pages[0] = all_buf + PAGE_SIZE;
> > rb->page_order = ilog2(nr_pages);
> > - rb->nr_pages = 1;
> > + rb->nr_pages = nr_pages;
> >
>
> hum, and this ^^^ breaks perf_data_size(rb) ;)
>
> static inline unsigned long perf_data_size(struct ring_buffer *rb)
> {
> return rb->nr_pages << (PAGE_SHIFT + page_order(rb));
> }

How so? 0 << n keeps being 0, right?

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