Re: [PATCH v7 0/8] x86/module: use large ROX pages for text allocations

Mike Rapoport
2024-11-18T18:40:29Z

On Mon, Nov 18, 2024 at 01:25:01PM -0500, Steven Rostedt wrote:
> On Wed, 23 Oct 2024 19:27:03 +0300
> Mike Rapoport <rppt@kernel.org> wrote:
>
> > From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> >
> > Hi,
> >
> > This is an updated version of execmem ROX caches.
> >
>
> FYI, I booted a kernel before and after applying these patches with my
> change:
>
> https://lore.kernel.org/20241017113105.1edfa943@gandalf.local.home
>
> Before these patches:
>
> # cat /sys/kernel/tracing/dyn_ftrace_total_info
> 57695 pages:231 groups: 9
> ftrace boot update time = 14733459 (ns)
> ftrace module total update time = 449016 (ns)
>
> After:
>
> # cat /sys/kernel/tracing/dyn_ftrace_total_info
> 57708 pages:231 groups: 9
> ftrace boot update time = 47195374 (ns)
> ftrace module total update time = 592080 (ns)
>
> Which caused boot time to slowdown by over 30ms. That may not seem like
> much, but we are very concerned about boot time and are fighting every ms
> we can get.

Hmm, looks like this change was lost in rebase :/

@Andrew, should I send it as a patch on top of mm-stable?

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 8da0e66ca22d..859902dd06fc 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -111,17 +111,22 @@ static int ftrace_verify_code(unsigned long ip, const char *old_code)
*/
static int __ref
ftrace_modify_code_direct(unsigned long ip, const char *old_code,
- const char *new_code)
+ const char *new_code, struct module *mod)
{
int ret = ftrace_verify_code(ip, old_code);
if (ret)
return ret;

/* replace the text with the new text */
- if (ftrace_poke_late)
+ if (ftrace_poke_late) {
text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
- else
+ } else if (!mod) {
text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
+ } else {
+ mutex_lock(&text_mutex);
+ text_poke((void *)ip, new_code, MCOUNT_INSN_SIZE);
+ mutex_unlock(&text_mutex);
+ }
return 0;
}

@@ -142,7 +147,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long ad
* just modify the code directly.
*/
if (addr == MCOUNT_ADDR)
- return ftrace_modify_code_direct(ip, old, new);
+ return ftrace_modify_code_direct(ip, old, new, mod);

/*
* x86 overrides ftrace_replace_code -- this function will never be used
@@ -161,7 +166,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
new = ftrace_call_replace(ip, addr);

/* Should only be called when module is loaded */
- return ftrace_modify_code_direct(rec->ip, old, new);
+ return ftrace_modify_code_direct(rec->ip, old, new, NULL);
}

/*

> -- Steve

--
Sincerely yours,
Mike.