Commit b40c6eab authored Aug 31, 2020 by Wei Yang Committed by Steven Rostedt (VMware) Oct 08, 2020

ftrace: Simplify the calculation of page number for ftrace_page->records

Based on the following two reasones, we could simplify the calculation:

  - If the number after roundup count is not power of 2, we would
    definitely have more than 1 empty page with a higher order.
  - get_count_order() just return current order, so one lower order
    could meet the requirement.

The calculation could be simplified by lower one order level when pages
are not power of 2.

Link: https://lkml.kernel.org/r/20200831031104.23322-5-richard.weiyang@linux.alibaba.com



Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 02dae28f

kernel/trace/ftrace.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -3129,18 +3129,19 @@ static int ftrace_update_code(struct module mod, struct ftrace_page new_pgs)
		static int ftrace_allocate_records(struct ftrace_page *pg, int count)
		{
		int order;
		int cnt;
		int pages, cnt;

		if (WARN_ON(!count))
		return -EINVAL;

		order = get_count_order(DIV_ROUND_UP(count, ENTRIES_PER_PAGE));
		pages = DIV_ROUND_UP(count, ENTRIES_PER_PAGE);
		order = get_count_order(pages);

		/*
		* We want to fill as much as possible. No more than a page
		* may be empty.
		*/
		while ((PAGE_SIZE << order) / ENTRY_SIZE >= count + ENTRIES_PER_PAGE)
		if (!is_power_of_2(pages))
		order--;

		again:

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