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

[Mike Rapoport]

On Mon, Nov 18, 2024 at 01:25:01PM -0500, Steven Rostedt wrote:
> On Wed, 23 Oct 2024 19:27:03 +0300
> Mike Rapoport <r...@kernel.org> wrote:
> 
> > From: "Mike Rapoport (Microsoft)" <r...@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/20241017113105.1edfa...@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.