From: Ryan Roberts Date: Mon, 21 Oct 2024 14:18:31 +0000 (+0100) Subject: tracing: Make percpu stack trace buffer invariant to PAGE_SIZE X-Git-Tag: v6.13-rc1~115^2~14 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=2c33155ef678033b8a3105b824cdef930f05b47d;p=linux-block.git tracing: Make percpu stack trace buffer invariant to PAGE_SIZE Previously the size of "struct ftrace_stacks" depended upon PAGE_SIZE. For the common 4K page size, on a 64-bit system, sizeof(struct ftrace_stacks) was 32K. But for a 64K page size, sizeof(struct ftrace_stacks) was 512K. But ftrace stack usage requirements should be invariant to page size. So let's redefine FTRACE_KSTACK_ENTRIES so that "struct ftrace_stacks" is always sized at 32K for 64-bit and 16K for 32-bit. As a side effect, it removes the PAGE_SIZE compile-time constant assumption from this code, which is required to reach the goal of boot-time page size selection. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20241021141832.3668264-1-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Signed-off-by: Steven Rostedt (Google) --- diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index bdb776e6ceb9..f1d613d924e9 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2898,7 +2898,7 @@ trace_function(struct trace_array *tr, unsigned long ip, unsigned long /* Allow 4 levels of nesting: normal, softirq, irq, NMI */ #define FTRACE_KSTACK_NESTING 4 -#define FTRACE_KSTACK_ENTRIES (PAGE_SIZE / FTRACE_KSTACK_NESTING) +#define FTRACE_KSTACK_ENTRIES (SZ_4K / FTRACE_KSTACK_NESTING) struct ftrace_stack { unsigned long calls[FTRACE_KSTACK_ENTRIES];