| Message ID | 20241021141832.3668264-1-ryan.roberts@arm.com (mailing list archive) |
|---|---|
| State | Queued |
| Headers | show |
| Series | [v2] tracing: Make percpu stack trace buffer invariant to PAGE_SIZE | expand |
On 21/10/2024 15:18, Ryan Roberts wrote: > 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. Just a polite bump on this... Does anyone have any comments? Thanks, Ryan > > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> > --- > kernel/trace/trace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 1c69ca1f1088..d4654943b580 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -2914,7 +2914,7 @@ 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]; > -- > 2.43.0 >
On Wed, 30 Oct 2024 08:50:16 +0000 Ryan Roberts <ryan.roberts@arm.com> wrote: > On 21/10/2024 15:18, Ryan Roberts wrote: > > 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. > > Just a polite bump on this... Does anyone have any comments? No, it's in my queue. I've just been traveling. -- Steve
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 1c69ca1f1088..d4654943b580 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2914,7 +2914,7 @@ 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];
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. Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> --- kernel/trace/trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.43.0