Re: [PATCH] enable/disable profiling via proc/sysctl

[Levent Serinol <lserinol@gmail.com>]

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Hi Andrew,

 The fixed patch is attached. I hope, it's ok this time. 

Thanks,


On 6/27/05, Andrew Morton <akpm@osdl.org> wrote:
> Levent Serinol <lserinol@gmail.com> wrote:
> >
> > This patch enables controlling kernel profiling through proc/sysctl inferface.
> >
> >  With this patch profiling will be available without rebooting the
> >  machine (especially for
> >  production servers) with some drawbacks of vmalloc(tlb). So, bootime
> >  algorithm part is left unchanged for anyone who wishes to use
> >  profiling as usual without tlb drawback by rebooting the machine.
> 
> 
> > --- include/linux/sysctl.h.org        2005-06-13 16:05:17.000000000 +0300
> > +++ include/linux/sysctl.h    2005-06-25 15:05:06.000000000 +0300
> 
> Patches should be in `patch -p1' form, please.  See
> http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt
> 
> > +static int prof_on = 0;
> > +static int prof_booton = 0;
> 
> There's no need to explicitly initialise these.
> 
> > +#ifdef CONFIG_SMP
> > +static int remove_hash_tables(void)
> > +{
> > +     int cpu;
> > +
> > +     smp_mb();
> > +     on_each_cpu(profile_nop, NULL, 0, 1);
> 
> Why?
> 
> > +     for_each_online_cpu(cpu) {
> > +             struct page *page;
> > +
> > +             if (per_cpu(cpu_profile_hits, cpu)[0]) {
> > +                     page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
> > +                     per_cpu(cpu_profile_hits, cpu)[0] = NULL;
> > +                     __free_page(page);
> > +             }
> > +             if (per_cpu(cpu_profile_hits, cpu)[1]) {
> > +                     page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
> > +                     per_cpu(cpu_profile_hits, cpu)[1] = NULL;
> > +                     __free_page(page);
> > +             }
> > +     }
> 
> Can this race against itself?  If two cpus run the sysctl at the same time?
> We seem to have lock_kernel() coverage.  It's be nice to do something
> firmer.
> 
> > +int profile_sysctl_handler(ctl_table *table, int write,
> > +     struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
> > +{
> > +     int err;
> > +     struct proc_dir_entry *entry;
> > +
> > +     if (prof_booton && write) return 0;
> > +     err=proc_dointvec(table, write, file, buffer, length, ppos);
> > +     if ((err >= 0) && write) {
> > +     prof_shift = profile_params[1];
> > +     switch(profile_params[0])
> > +     {
> > +     case 0:
> > +             if (prof_on) {
> 
> Coding style is all over the place here, as well as in most of the rest of
> the patch.
> 
> 
>         if (prof_booton && write)
>                 return 0;
>         err = proc_dointvec(table, write, file, buffer, length, ppos);
>         if (err >= 0 && write) {
>                 prof_shift = profile_params[1];
>                 switch (profile_params[0])
>                 {
>                 case 0:
>                         if (prof_on) {
> 
> Every line was changed there...
> 
> Also, doing multiple returns per function is unpopular, although the
> very-early
> 
>         if (foo)
>                 return <something>;
> 
> right at the top of the function is OK.  You can use
> 
>         if (err < 0 || !write)
>                 goto out;
> 
> to save a tab stop.
> 
> > +                  }
> > +             break;
> 
>                 }
>                 break;
> 
> > +     case SCHED_PROFILING || CPU_PROFILING:
> 
> eh?  I'm surprised the compiler swallowed that.  I guess it's the same as
> `case 1:'.  Looks like a bug though.
> 
> > +             if (prof_on) return -1;
> > +             prof_len = (_etext - _stext) >> prof_shift;
> > +             prof_buffer = vmalloc(prof_len*sizeof(atomic_t));
> > +             if (!prof_buffer) return(-ENOMEM);
> > +             if (create_hash_tables()) {
> > +                     vfree(prof_buffer);
> > +                     return -1;
> > +                     }
> > +             prof_on = profile_params[0];
> > +             if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL))) {
> > +                     remove_hash_tables();
> > +                     vfree(prof_buffer);
> > +                     return 0;
> > +                     }
> > +             entry->proc_fops = &proc_profile_operations;
> > +             entry->size = (1+prof_len) * sizeof(atomic_t);
> > +#ifdef CONFIG_HOTPLUG_CPU
> > +             register_cpu_notifier(&profile_cpu_notifier);
> > +#endif
> > +             profile_discard_flip_buffers();
> > +             memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
> > +                     switch(prof_on)
> > +                     {
> > +                     case SCHED_PROFILING:printk(KERN_INFO
> > +                             "kernel schedule profiling enabled (shift: %ld)\n",
> > +                             prof_shift);
> > +                             break;
> > +                     case CPU_PROFILING:printk(KERN_INFO
> > +                             "kernel profiling enabled (shift: %ld)\n",
> > +                             prof_shift);
> > +                             break;
> > +                             }
> > +                     break;
> > +                     }
> > +             }
> > +     return 0;
> > +}
> 
> Documentation/CodingStyle is your friend ;)
> 
> > --- kernel/sysctl.c.org       2005-06-13 16:05:23.000000000 +0300
> > +++ kernel/sysctl.c   2005-06-26 02:06:23.000000000 +0300
> > ...
> > +extern int profile_params[];
> 
> Try to place this declaration in a header.
> 
> What locking protects prof_boot_on()?  lock_kernel() won't be sufficient
> because we're doing sleeping allocations in here.
> 
> I suspect it would be best to whap a semaphore around the whole thing.
> 


-- 

Stay out of the road, if you want to grow old. 
~ Pink Floyd ~.

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[-- Attachment #2: profile.patch --]
[-- Type: text/x-patch; name="profile.patch", Size: 6975 bytes --]

diff -uprN -X dontdiff linux-2.6.12-rc6.orig/include/linux/profile.h linux-2.6.12-rc6/include/linux/profile.h
--- linux-2.6.12-rc6.orig/include/linux/profile.h	2005-03-02 09:38:08.000000000 +0200
+++ linux-2.6.12-rc6/include/linux/profile.h	2005-06-27 10:19:43.000000000 +0300
@@ -6,14 +6,21 @@
 #include <linux/kernel.h>
 #include <linux/config.h>
 #include <linux/init.h>
+#include <linux/sysctl.h>
 #include <linux/cpumask.h>
 #include <asm/errno.h>
 
 #define CPU_PROFILING	1
 #define SCHED_PROFILING	2
 
+struct ctl_table;
+struct file;
 struct proc_dir_entry;
 struct pt_regs;
+extern int profile_params[];
+int profile_sysctl_handler(ctl_table *table, int write,
+               struct file *file, void __user *buffer, size_t
+*length, loff_t *ppos);
 
 /* init basic kernel profiler */
 void __init profile_init(void);
diff -uprN -X dontdiff linux-2.6.12-rc6.orig/include/linux/sysctl.h linux-2.6.12-rc6/include/linux/sysctl.h
--- linux-2.6.12-rc6.orig/include/linux/sysctl.h	2005-06-27 15:06:23.000000000 +0300
+++ linux-2.6.12-rc6/include/linux/sysctl.h	2005-06-27 10:15:54.000000000 +0300
@@ -136,6 +136,7 @@ enum
 	KERN_UNKNOWN_NMI_PANIC=66, /* int: unknown nmi panic flag */
 	KERN_BOOTLOADER_TYPE=67, /* int: boot loader type */
 	KERN_RANDOMIZE=68, /* int: randomize virtual address space */
+	KERN_PROFILE=69, /* int: profile on/off */
 };
 
 
diff -uprN -X dontdiff linux-2.6.12-rc6.orig/kernel/profile.c linux-2.6.12-rc6/kernel/profile.c
--- linux-2.6.12-rc6.orig/kernel/profile.c	2005-06-27 15:06:23.000000000 +0300
+++ linux-2.6.12-rc6/kernel/profile.c	2005-06-27 15:05:07.000000000 +0300
@@ -21,7 +21,6 @@
 #include <linux/mm.h>
 #include <linux/cpumask.h>
 #include <linux/cpu.h>
-#include <linux/profile.h>
 #include <linux/highmem.h>
 #include <asm/sections.h>
 #include <asm/semaphore.h>
@@ -37,9 +36,12 @@ struct profile_hit {
 /* Oprofile timer tick hook */
 int (*timer_hook)(struct pt_regs *);
 
+struct semaphore prof_sem;
+int profile_params[2] = {0, 0};
 static atomic_t *prof_buffer;
 static unsigned long prof_len, prof_shift;
 static int prof_on;
+static int prof_booton;
 static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
 #ifdef CONFIG_SMP
 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
@@ -74,12 +76,14 @@ __setup("profile=", profile_setup);
 
 void __init profile_init(void)
 {
+	init_MUTEX(&prof_sem);
 	if (!prof_on) 
 		return;
  
 	/* only text is profiled */
 	prof_len = (_etext - _stext) >> prof_shift;
 	prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
+	prof_booton = 1;
 }
 
 /* Profile event notifications */
@@ -367,6 +371,12 @@ static int __devinit profile_cpu_callbac
 	}
 	return NOTIFY_OK;
 }
+static struct notifier_block profile_cpu_notifier =
+{
+         .notifier_call = profile_cpu_callback,
+         .priority = 0,
+};
+
 #endif /* CONFIG_HOTPLUG_CPU */
 #else /* !CONFIG_SMP */
 #define profile_flip_buffers()		do { } while (0)
@@ -500,11 +510,11 @@ static struct file_operations proc_profi
 };
 
 #ifdef CONFIG_SMP
-static void __init profile_nop(void *unused)
+static void profile_nop(void *unused)
 {
 }
 
-static int __init create_hash_tables(void)
+int create_hash_tables(void)
 {
 	int cpu;
 
@@ -548,6 +558,104 @@ out_cleanup:
 #define create_hash_tables()			({ 0; })
 #endif
 
+#ifdef CONFIG_SMP
+int remove_hash_tables(void)
+{
+	int cpu;
+
+
+	for_each_online_cpu(cpu) {
+		struct page *page;
+
+		if (per_cpu(cpu_profile_hits, cpu)[0]) {
+			page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
+			per_cpu(cpu_profile_hits, cpu)[0] = NULL;
+			__free_page(page);
+		}
+		if (per_cpu(cpu_profile_hits, cpu)[1]) {
+			page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
+			per_cpu(cpu_profile_hits, cpu)[1] = NULL;
+			__free_page(page);
+		}
+	}
+	return -1;
+}
+#else
+#define remove_hash_tables()			({ 0; })
+#endif
+
+int profile_sysctl_handler(ctl_table *table, int write, struct file *file, 
+		void __user *buffer, size_t *length, loff_t *ppos)
+{
+	int err;
+	struct proc_dir_entry *entry;
+
+
+	down(&prof_sem);
+
+	if (prof_booton && write) 
+		goto out;
+
+	err=proc_dointvec(table, write, file, buffer, length, ppos);
+	if (err < 0 || !write)
+		goto out;
+
+	prof_shift = profile_params[1];
+
+	if (!profile_params[0]) {
+		if (prof_on) {
+			prof_on = 0;
+			remove_proc_entry("profile",NULL);
+#ifdef CONFIG_HOTPLUG_CPU
+			unregister_cpu_notifier(&profile_cpu_notifier);
+#endif
+			remove_hash_tables();
+			vfree(prof_buffer);
+			printk(KERN_INFO "kernel profiling disabled\n");
+		}
+	}
+
+	if ((profile_params[0]==SCHED_PROFILING) || (profile_params[0]==CPU_PROFILING)) {
+		if (prof_on)
+			goto out;
+        	prof_len = (_etext - _stext) >> prof_shift;
+        	prof_buffer = vmalloc(prof_len*sizeof(atomic_t));
+		if (!prof_buffer)
+			goto out;
+		if (create_hash_tables()) {
+			vfree(prof_buffer);
+			goto out;
+		}
+		prof_on = profile_params[0];
+		if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL))) {
+			remove_hash_tables();
+			vfree(prof_buffer);
+			goto out;
+		}
+		entry->proc_fops = &proc_profile_operations;
+		entry->size = (1+prof_len) * sizeof(atomic_t);
+#ifdef CONFIG_HOTPLUG_CPU
+		register_cpu_notifier(&profile_cpu_notifier);
+#endif
+		profile_discard_flip_buffers();
+        	memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
+			switch(prof_on) {
+			case SCHED_PROFILING:
+				printk(KERN_INFO "kernel schedule profiling enabled (shift: %ld)\n",
+						prof_shift);
+				break;
+			case CPU_PROFILING:
+				printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
+						prof_shift);
+				break;
+			} 
+	}
+
+out:
+	up(&prof_sem);
+	return 0;
+}
+
 static int __init create_proc_profile(void)
 {
 	struct proc_dir_entry *entry;
@@ -560,7 +668,11 @@ static int __init create_proc_profile(vo
 		return 0;
 	entry->proc_fops = &proc_profile_operations;
 	entry->size = (1+prof_len) * sizeof(atomic_t);
-	hotcpu_notifier(profile_cpu_callback, 0);
+#ifdef CONFIG_HOTPLUG_CPU
+	register_cpu_notifier(&profile_cpu_notifier);
+#endif
+	profile_params[0] = prof_on;
+	profile_params[1] = prof_shift;
 	return 0;
 }
 module_init(create_proc_profile);
diff -uprN -X dontdiff linux-2.6.12-rc6.orig/kernel/sysctl.c linux-2.6.12-rc6/kernel/sysctl.c
--- linux-2.6.12-rc6.orig/kernel/sysctl.c	2005-06-27 15:06:23.000000000 +0300
+++ linux-2.6.12-rc6/kernel/sysctl.c	2005-06-27 10:19:07.000000000 +0300
@@ -21,6 +21,7 @@
 #include <linux/config.h>
 #include <linux/module.h>
 #include <linux/mm.h>
+#include <linux/profile.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
 #include <linux/sysctl.h>
@@ -642,7 +643,15 @@ static ctl_table kern_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
-
+	{
+		.ctl_name       = KERN_PROFILE,
+		.procname       = "profile",
+		.data           = &profile_params,
+		.maxlen         = 2*sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = &profile_sysctl_handler,
+		.strategy       = &sysctl_intvec,
+	},
 	{ .ctl_name = 0 }
 };