Re: [RFC][PATCH 2.6.11-rc3-mm2] Relay Fork Module
From: Guillaume Thouvenin
Date: Fri Feb 11 2005 - 10:16:43 EST
On Fri, 2005-02-11 at 00:54 -0800, Andrew Morton wrote:
> > I tested this patch on a 2.6.11-rc3-mm2 kernel and there is a little
> > overhead when I compile a Linux kernel:
> >
> > #time sh -c 'make O=/home/guill/build/k2610 bzImage &&
> > make O=/home/guill/build/k2610 modules'
> >
> > with a vanilla kernel: real 8m10.797s
> > user 7m29.652s
> > sys 0m49.275s
> >
> > with the forkuevent patch : real 8m16.189s
> > user 7m28.841s
> > sys 0m49.155s
>
> Was that when some process was monitoring the netlink socket?
I used another patch for running those tests and here are the changes:
- struct kobject fork_kobjet is now static
- add a test that drop the construction of the message nobody is
listening on the netlink.
- put the code in a #ifdef CONFIG_KOBJECT_UEVENT section but I
directly add the #ifdef in the code instead of moving the code in
the existing #ifdef CONFIG_KOBJECT_UEVENT section.
There are still some open discussions like the duplicate code and the
use of the kobject here. I continue to work on that.
Here are results about performance impact. The test is the compilation
of 2.6.10 kernel. For monitoring the KOBJ_FORK event I'm using the
uevent_listen.c written by Kay Sievers. Three situation was tested:
1) Vanilla 2.6.11-rc3-mm2 kernel
2) 2.6.11-rc3-mm2 + patch (without monitoring)
3) 2.6.11-rc3-mm2 + patch + monitoring
command used :
# time sh -c 'make O=/home/guill/build/k2610 oldconfig && \
make O=/home/guill/build/k2610 bzImage && \
make O=/home/guill/build/k2610 modules'
Between each test the directory /home/guill/build/k2610 was destroyed,
a new one was created, a .config file was copied in the directory and
file system buffers are flushed with 'sync'. Here are the results:
| Real User Sys |
-----------|-----------------------------------|
Vanilla | 8m06.808s 7m32.044s 0m51.647s |
| 8m07.144s 7m32.804s 0m51.308s |
| 8m06.856s 7m31.414s 0m51.711s |
| 8m06.875s 7m32.082s 0m51.885s |
| 8m07.205s 7m32.140s 0m51.766s |
-----------|-----------------------------------|
Kernel + | 8m15.884s 7m31.838s 0m50.616s |
Patch | 8m08.506s 7m34.154s 0m51.005s |
| 8m07.972s 7m33.761s 0m51.416s |
| 8m08.006s 7m33.683s 0m51.206s |
| 8m09.138s 7m34.212s 0m51.087s |
-----------|-----------------------------------|
Kernel + | 8m08.149s 7m33.590s 0m51.527s |
Patch + | 8m08.595s 7m33.674s 0m51.380s |
Monitoring | 8m08.374s 7m34.011s 0m51.282s |
| 8m09.317s 7m34.563s 0m51.259s |
| 8m08.121s 7m35.412s 0m51.069s |
-----------------------------------------------/
Regards,
Guillaume
Signed-off-by: Guillaume Thouvenin <guillaume.thouvenin@xxxxxxxx>
diff -uprN -X dontdiff linux-2.6.11-rc3-mm2/include/linux/kobject.h linux-2.6.11-rc3-mm2-forkuevent/include/linux/kobject.h
--- linux-2.6.11-rc3-mm2/include/linux/kobject.h 2005-02-03 02:54:59.000000000 +0100
+++ linux-2.6.11-rc3-mm2-forkuevent/include/linux/kobject.h 2005-02-11 11:03:13.000000000 +0100
@@ -253,5 +253,7 @@ static inline int add_hotplug_env_var(ch
{ return 0; }
#endif
+extern void kobject_fork(struct kobject *, pid_t, pid_t);
+
#endif /* __KERNEL__ */
#endif /* _KOBJECT_H_ */
diff -uprN -X dontdiff linux-2.6.11-rc3-mm2/include/linux/kobject_uevent.h linux-2.6.11-rc3-mm2-forkuevent/include/linux/kobject_uevent.h
--- linux-2.6.11-rc3-mm2/include/linux/kobject_uevent.h 2005-02-03 02:54:38.000000000 +0100
+++ linux-2.6.11-rc3-mm2-forkuevent/include/linux/kobject_uevent.h 2005-02-11 11:03:44.000000000 +0100
@@ -29,6 +29,7 @@ enum kobject_action {
KOBJ_UMOUNT = (__force kobject_action_t) 0x05, /* umount event for block devices */
KOBJ_OFFLINE = (__force kobject_action_t) 0x06, /* offline event for hotplug devices */
KOBJ_ONLINE = (__force kobject_action_t) 0x07, /* online event for hotplug devices */
+ KOBJ_FORK = (__force kobject_action_t) 0x08, /* a child process has been created */
};
diff -uprN -X dontdiff linux-2.6.11-rc3-mm2/kernel/fork.c linux-2.6.11-rc3-mm2-forkuevent/kernel/fork.c
--- linux-2.6.11-rc3-mm2/kernel/fork.c 2005-02-11 11:00:18.000000000 +0100
+++ linux-2.6.11-rc3-mm2-forkuevent/kernel/fork.c 2005-02-11 11:05:43.000000000 +0100
@@ -41,6 +41,7 @@
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/acct.h>
+#include <linux/kobject.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -57,6 +58,9 @@ int nr_threads; /* The idle threads do
int max_threads; /* tunable limit on nr_threads */
+/* kobject used to notify user space application when a fork occurs */
+static struct kobject fork_kobj;
+
DEFINE_PER_CPU(unsigned long, process_counts) = 0;
__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
@@ -148,6 +152,13 @@ void __init fork_init(unsigned long memp
init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
+
+ /*
+ * We init the fork_kobj which is the event sends when a fork
+ * occurs.
+ */
+ kobject_init(&fork_kobj);
+ kobject_set_name(&fork_kobj, "fork_kobj");
}
static struct task_struct *dup_task_struct(struct task_struct *orig)
@@ -1238,6 +1249,8 @@ long do_fork(unsigned long clone_flags,
if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
}
+
+ kobject_fork(&fork_kobj, current->pid, p->pid);
} else {
free_pidmap(pid);
pid = PTR_ERR(p);
diff -uprN -X dontdiff linux-2.6.11-rc3-mm2/lib/kobject_uevent.c linux-2.6.11-rc3-mm2-forkuevent/lib/kobject_uevent.c
--- linux-2.6.11-rc3-mm2/lib/kobject_uevent.c 2005-02-11 11:00:18.000000000 +0100
+++ linux-2.6.11-rc3-mm2-forkuevent/lib/kobject_uevent.c 2005-02-11 11:08:23.000000000 +0100
@@ -46,6 +46,8 @@ static char *action_to_string(enum kobje
return "offline";
case KOBJ_ONLINE:
return "online";
+ case KOBJ_FORK:
+ return "fork";
default:
return NULL;
}
@@ -433,3 +435,69 @@ int add_hotplug_env_var(char **envp, int
EXPORT_SYMBOL(add_hotplug_env_var);
#endif /* CONFIG_HOTPLUG */
+
+/*
+ * The buffer will contain 1 integer which has 20 digits for
+ * 64 bits integer. So a size of 32 is large enough...
+ */
+#define FORK_BUFFER_SIZE 32
+
+/*
+ * number of env pointers is set to FORK_BUFFER_NB
+ * env[0] - Not used
+ * env[1] - Not used
+ * env[2] - parent pid
+ * env[3] - child pid
+ * env[4] - NULL
+ */
+#define FORK_BUFFER_NB 5
+
+/**
+ * kobject_fork - notify userspace when forking
+ *
+ * @kobj: struct kobject that the action is happening to
+ */
+void kobject_fork(struct kobject *kobj, pid_t parent, pid_t child)
+{
+#ifdef CONFIG_KOBJECT_UEVENT
+ char *kobj_path = NULL;
+ char *action_string = NULL;
+ char **envp = NULL;
+ char ppid_string[FORK_BUFFER_SIZE];
+ char cpid_string[FORK_BUFFER_SIZE];
+
+ if (!uevent_sock)
+ return;
+
+ action_string = action_to_string(KOBJ_FORK);
+ if (!action_string)
+ return;
+
+ kobj_path = kobject_get_path(kobj, GFP_KERNEL);
+ if (!kobj_path)
+ return;
+
+ envp = kmalloc(FORK_BUFFER_NB * sizeof (char *), GFP_KERNEL);
+ if (!envp) {
+ kfree(kobj_path);
+ return;
+ }
+ memset (envp, 0x0, FORK_BUFFER_NB * sizeof (char *));
+
+ snprintf(ppid_string, FORK_BUFFER_SIZE, "%i", parent);
+ snprintf(cpid_string, FORK_BUFFER_SIZE, "%i", child);
+
+ envp[0] = "Not used";
+ envp[1] = "Not used";
+ envp[2] = ppid_string;
+ envp[3] = cpid_string;
+ envp[4] = NULL;
+
+ send_uevent(action_string, kobj_path, envp, GFP_KERNEL);
+
+ kfree(envp);
+ kfree(kobj_path);
+#endif /* CONFIG_KOBJECT_UEVENT */
+ return;
+}
+EXPORT_SYMBOL(kobject_fork);
-
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