Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Michael Kerrisk]

[Fixing the bad list address in my initial mail: CC += linux-mm@kvack.org]

On Tue, May 20, 2008 at 4:45 PM, Nadia Derbey <Nadia.Derbey@bull.net> wrote:
> Michael Kerrisk wrote:
>>
>> Hello Nadia,
>>
>> Regarding your:
>>
>> [PATCH 1/8] Scaling msgmni to the amount of lowmem
>> http://article.gmane.org/gmane.linux.kernel/637849/
>> which I see has made its way in 2.6.26-rc
>>
>> Your patch has the following change:
>>
>> -#define MSGPOOL (MSGMNI*MSGMNB/1024)  /* size in kilobytes of message
>> pool */
>> +#define MSGPOOL (MSGMNI * MSGMNB) /* size in bytes of message pool */
>>
>> Since this constitutes a kernel-userland interface change, so please
>> do CC me, so that I can change the man pages if needed.
>
> Oops, sorry for not doing it: I misunderstood the "unused"
>
>>
>> The man page
>> (http://www.kernel.org/doc/man-pages/online/pages/man2/msgctl.2.html)
>> does indeed say that msgpool is "unused".  But that meant "unused by
>> the kernel" (sorry -- I probably should have worded that text better).
>>  And, as you spotted, the page also wrongly said the value is in
>> bytes.
>>
>> However, making this change affects the ABI.  A userspace application
>> that was previously using msgctl(IPC_INFO) to retrieve the msgpool
>> field will be affected by the factor-of-1024 change.  I strongly
>> suspect that there no such applications, or certainly none that care
>> (since this value is unused by the kernel).  But was there a reason
>> for making this change, aside from the fact that the code and the man
>> page didn't agree?
>>
>
> No, that was the only reason.
> Should I repost a patch to set it back as it used to be?

On the one hand, I'd be inclined to leave things as they were pre
2.6.26.  On the other hand, I believe that on other systems that have
the limit, msgpool is a limit in bytes.  (But documentation of these
details on other systems is very thin on the ground.)  I wonder if
anyone else has some knowledge here?


-- 
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Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Michael Kerrisk]

On Tue, May 20, 2008 at 4:45 PM, Nadia Derbey <Nadia.Derbey@bull.net> wrote:
> Michael Kerrisk wrote:
>>
>> Hello Nadia,
>>
>> Regarding your:
>>
>> [PATCH 1/8] Scaling msgmni to the amount of lowmem
>> http://article.gmane.org/gmane.linux.kernel/637849/
>> which I see has made its way in 2.6.26-rc
>>
>> Your patch has the following change:
>>
>> -#define MSGPOOL (MSGMNI*MSGMNB/1024)  /* size in kilobytes of message
>> pool */
>> +#define MSGPOOL (MSGMNI * MSGMNB) /* size in bytes of message pool */
>>
>> Since this constitutes a kernel-userland interface change, so please
>> do CC me, so that I can change the man pages if needed.
>
> Oops, sorry for not doing it: I misunderstood the "unused"
>
>>
>> The man page
>> (http://www.kernel.org/doc/man-pages/online/pages/man2/msgctl.2.html)
>> does indeed say that msgpool is "unused".  But that meant "unused by
>> the kernel" (sorry -- I probably should have worded that text better).
>>  And, as you spotted, the page also wrongly said the value is in
>> bytes.
>>
>> However, making this change affects the ABI.  A userspace application
>> that was previously using msgctl(IPC_INFO) to retrieve the msgpool
>> field will be affected by the factor-of-1024 change.  I strongly
>> suspect that there no such applications, or certainly none that care
>> (since this value is unused by the kernel).  But was there a reason
>> for making this change, aside from the fact that the code and the man
>> page didn't agree?
>>
>
> No, that was the only reason.
> Should I repost a patch to set it back as it used to be?

Nadia,

I think for the moment it might be best to revert that change, since
there's no actual need to change things.  I've updated the man page to
say that this value is in kibibytes.

Cheers,

Michael

-- 
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Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html

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[PATCH 0/8] Change default MSGMNI tunable to scale with lowmem (v3)

[Nadia.Derbey]

Resending the set of patches after Yasunori's remark about being able to
turn on/off automatic recomputing.
(see message at http://lkml.org/lkml/2008/2/5/149).
I actually introduced an intermediate solution: when msgmni is set by hand,
it is uneregistered from the ipcns notifier chain (i.e. automatic recomputing
is disabled). This corresponds to an implicit turn off. Setting it to a
negative value makes it registered back in the notifier chain (which
corresponds to the turn on proposed by Yasunaori).

Only patch # 8 introduces new stuff compared to the already sent patch sets.

Also ported the patchset to 2.6.24-mm1.

-------------------

On large systems we'd like to allow a larger number of message queues.
In some cases up to 32K. However simply setting MSGMNI to a larger value may
cause problems for smaller systems.

The first patch of this series introduces a default maximum number of message
queue ids that scales with the amount of lowmem.

Since msgmni is per namespace and there is no amount of memory dedicated to
each namespace so far, the second patch of this series scales msgmni to
the number of ipc namespaces too.

Since msgmni depends on the amount of memory, it becomes necessary to
recompute it upon memory add/remove.
In the 4th patch, memory hotplug management is added: a notifier block is
registered into the memory hotplug notifier chain for the ipc subsystem.
Since the ipc namespaces are not linked together, they have their own
notification chain: one notifier_block is defined per ipc namespace.
Each time an ipc namespace is created (removed) it registers (unregisters)
its notifier block in (from) the ipcns chain.
The callback routine registered in the memory chain invokes the ipcns
notifier chain with the IPCNS_MEMCHANGE event.
Each callback routine registered in the ipcns namespace, in turn, recomputes
msgmni for the owning namespace.

The 5th patch makes it possible to keep the memory hotplug notifier chain's
lock for a lesser amount of time: instead of directly notifying the ipcns
notifier chain upon memory add/remove, a work item is added to the global
workqueue. When activated, this work item is the one who notifies the ipcns
notifier chain.

Since msgmni depends on the number of ipc namespaces, it becomes necessary
to recompute it upon ipc namespace creation / removal.
The 6th patch uses the ipc namespace notifier chain for that purpose: that
chain is notified each time an ipc namespace is created or removed. This makes
it possible to recompute msgmni for all the namespaces each time one of them
is created or removed.

When msgmni is explicitely set from userspace, we should avoid recomputing it
upon memory add/remove or ipcns creation/removal.
This is what the 7th patch does: it simply unregisters the ipcns callback
routine as soon as msgmni has been changed from procfs or sysctl().

Even if msgmni is set by hand, it should be possible to make it back
automatically recomputed upon memory add/remove or ipcns creation/removal.
This what is achieved in patch 8: if set to a negative value, msgmni is added
back to the ipcns notifier chain, making it automatically recomputed again.


These patches should be applied to 2.6.24-mm1, in the following order:

[PATCH 1/8]: ipc_scale_msgmni_with_lowmem.patch
[PATCH 2/8]: ipc_scale_msgmni_with_namespaces.patch
[PATCH 3/8]: ipc_slab_memory_callback_prio_to_const.patch
[PATCH 4/8]: ipc_recompute_msgmni_on_memory_hotplug.patch
[PATCH 5/8]: ipc_ipcns_notification_workqueue.patch
[PATCH 6/8]: ipc_recompute_msgmni_on_ipcns_create_remove.patch
[PATCH 7/8]: ipc_unregister_callback_on_msgmni_manual_change.patch
[PATCH 8/8]: ipc_register_callback_on_negative_msgmni.patch


Andrew, do you think this patchset could be considered for inclusion in -mm
(or at least patches 1 to 6)?


Regards,
Nadia

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[PATCH 1/8] Scaling msgmni to the amount of lowmem

[Nadia.Derbey]

[-- Attachment #1: ipc_scale_msgmni_with_lowmem.patch --]
[-- Type: text/plain, Size: 3887 bytes --]

[PATCH 01/08]

This patch computes msg_ctlmni to make it scale with the amount of lowmem.
msg_ctlmni is now set to make the message queues occupy 1/32 of the available
lowmem.

Some cleaning has also been done for the MSGPOOL constant: the msgctl man page
says it's not used, but it also defines it as a size in bytes (the code
expresses it in Kbytes).

Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>

---
 include/linux/msg.h |   14 ++++++++++++--
 ipc/msg.c           |   37 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 48 insertions(+), 3 deletions(-)

Index: linux-2.6.24-mm1/include/linux/msg.h
===================================================================
--- linux-2.6.24-mm1.orig/include/linux/msg.h	2008-02-07 15:01:38.000000000 +0100
+++ linux-2.6.24-mm1/include/linux/msg.h	2008-02-07 15:23:17.000000000 +0100
@@ -49,16 +49,26 @@ struct msginfo {
 	unsigned short  msgseg; 
 };
 
+/*
+ * Scaling factor to compute msgmni:
+ * the memory dedicated to msg queues (msgmni * msgmnb) should occupy
+ * at most 1/MSG_MEM_SCALE of the lowmem (see the formula in ipc/msg.c):
+ * up to 8MB       : msgmni = 16 (MSGMNI)
+ * 4 GB            : msgmni = 8K
+ * more than 16 GB : msgmni = 32K (IPCMNI)
+ */
+#define MSG_MEM_SCALE 32
+
 #define MSGMNI    16   /* <= IPCMNI */     /* max # of msg queue identifiers */
 #define MSGMAX  8192   /* <= INT_MAX */   /* max size of message (bytes) */
 #define MSGMNB 16384   /* <= INT_MAX */   /* default max size of a message queue */
 
 /* unused */
-#define MSGPOOL (MSGMNI*MSGMNB/1024)  /* size in kilobytes of message pool */
+#define MSGPOOL (MSGMNI * MSGMNB) /* size in bytes of message pool */
 #define MSGTQL  MSGMNB            /* number of system message headers */
 #define MSGMAP  MSGMNB            /* number of entries in message map */
 #define MSGSSZ  16                /* message segment size */
-#define __MSGSEG ((MSGPOOL*1024)/ MSGSSZ) /* max no. of segments */
+#define __MSGSEG (MSGPOOL / MSGSSZ) /* max no. of segments */
 #define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)
 
 #ifdef __KERNEL__
Index: linux-2.6.24-mm1/ipc/msg.c
===================================================================
--- linux-2.6.24-mm1.orig/ipc/msg.c	2008-02-07 15:02:29.000000000 +0100
+++ linux-2.6.24-mm1/ipc/msg.c	2008-02-07 15:24:19.000000000 +0100
@@ -27,6 +27,7 @@
 #include <linux/msg.h>
 #include <linux/spinlock.h>
 #include <linux/init.h>
+#include <linux/mm.h>
 #include <linux/proc_fs.h>
 #include <linux/list.h>
 #include <linux/security.h>
@@ -78,11 +79,45 @@ static int newque(struct ipc_namespace *
 static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
 #endif
 
+/*
+ * Scale msgmni with the available lowmem size: the memory dedicated to msg
+ * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
+ * This should be done staying within the (MSGMNI , IPCMNI) range.
+ */
+static void recompute_msgmni(struct ipc_namespace *ns)
+{
+	struct sysinfo i;
+	unsigned long allowed;
+
+	si_meminfo(&i);
+	allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
+		/ MSGMNB;
+
+	if (allowed < MSGMNI) {
+		ns->msg_ctlmni = MSGMNI;
+		goto out_callback;
+	}
+
+	if (allowed > IPCMNI) {
+		ns->msg_ctlmni = IPCMNI;
+		goto out_callback;
+	}
+
+	ns->msg_ctlmni = allowed;
+
+out_callback:
+
+	printk(KERN_INFO "msgmni has been set to %d for ipc namespace %p\n",
+		ns->msg_ctlmni, ns);
+}
+
 void msg_init_ns(struct ipc_namespace *ns)
 {
 	ns->msg_ctlmax = MSGMAX;
 	ns->msg_ctlmnb = MSGMNB;
-	ns->msg_ctlmni = MSGMNI;
+
+	recompute_msgmni(ns);
+
 	atomic_set(&ns->msg_bytes, 0);
 	atomic_set(&ns->msg_hdrs, 0);
 	ipc_init_ids(&ns->ids[IPC_MSG_IDS]);

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Andrew Morton]

On Mon, 11 Feb 2008 15:16:47 +0100 Nadia.Derbey@bull.net wrote:

> [PATCH 01/08]
> 
> This patch computes msg_ctlmni to make it scale with the amount of lowmem.
> msg_ctlmni is now set to make the message queues occupy 1/32 of the available
> lowmem.
> 
> Some cleaning has also been done for the MSGPOOL constant: the msgctl man page
> says it's not used, but it also defines it as a size in bytes (the code
> expresses it in Kbytes).
> 

Something's wrong here.  Running LTP's msgctl08 (specifically:
ltp-full-20070228) cripples the machine.  It's a 4-way 4GB x86_64.

http://userweb.kernel.org/~akpm/config-x.txt
http://userweb.kernel.org/~akpm/dmesg-x.txt

Normally msgctl08 will complete in a second or two.  With this patch I
don't know how long it will take to complete, and the machine is horridly
bogged down.  It does recover if you manage to kill msgctl08.  Feels like
a terrible memory shortage, but there's plenty of memory free and it isn't
swapping.

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Nadia Derbey]

Andrew Morton wrote:
> On Mon, 11 Feb 2008 15:16:47 +0100 Nadia.Derbey@bull.net wrote:
> 
> 
>>[PATCH 01/08]
>>
>>This patch computes msg_ctlmni to make it scale with the amount of lowmem.
>>msg_ctlmni is now set to make the message queues occupy 1/32 of the available
>>lowmem.
>>
>>Some cleaning has also been done for the MSGPOOL constant: the msgctl man page
>>says it's not used, but it also defines it as a size in bytes (the code
>>expresses it in Kbytes).
>>
> 
> 
> Something's wrong here.  Running LTP's msgctl08 (specifically:
> ltp-full-20070228) cripples the machine.  It's a 4-way 4GB x86_64.
> 
> http://userweb.kernel.org/~akpm/config-x.txt
> http://userweb.kernel.org/~akpm/dmesg-x.txt
> 
> Normally msgctl08 will complete in a second or two.  With this patch I
> don't know how long it will take to complete, and the machine is horridly
> bogged down.  It does recover if you manage to kill msgctl08.  Feels like
> a terrible memory shortage, but there's plenty of memory free and it isn't
> swapping.
> 
> 
> 

Before the patchset, msgctl08 used to be run with the old msgmni value: 
16. Now it is run with a much higher msgmni value (1746 in my case), 
since it scales to the memory size.
When I call "msgctl08 100000 16" it completes fast.

Doing the follwing on the ref kernel:
echo 1746 > /proc/sys/kernel/msgmni
msgctl08 100000 1746

makes th test block too :-(

Will check to see where the problem comes from.

Rgards,
Nadia

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Nadia Derbey]

Nadia Derbey wrote:
> Andrew Morton wrote:
> 
>> On Mon, 11 Feb 2008 15:16:47 +0100 Nadia.Derbey@bull.net wrote:
>>
>>
>>> [PATCH 01/08]
>>>
>>> This patch computes msg_ctlmni to make it scale with the amount of 
>>> lowmem.
>>> msg_ctlmni is now set to make the message queues occupy 1/32 of the 
>>> available
>>> lowmem.
>>>
>>> Some cleaning has also been done for the MSGPOOL constant: the msgctl 
>>> man page
>>> says it's not used, but it also defines it as a size in bytes (the code
>>> expresses it in Kbytes).
>>>
>>
>>
>> Something's wrong here.  Running LTP's msgctl08 (specifically:
>> ltp-full-20070228) cripples the machine.  It's a 4-way 4GB x86_64.
>>
>> http://userweb.kernel.org/~akpm/config-x.txt
>> http://userweb.kernel.org/~akpm/dmesg-x.txt
>>
>> Normally msgctl08 will complete in a second or two.  With this patch I
>> don't know how long it will take to complete, and the machine is horridly
>> bogged down.  It does recover if you manage to kill msgctl08.  Feels like
>> a terrible memory shortage, but there's plenty of memory free and it 
>> isn't
>> swapping.
>>
>>
>>
> 
> Before the patchset, msgctl08 used to be run with the old msgmni value: 
> 16. Now it is run with a much higher msgmni value (1746 in my case), 
> since it scales to the memory size.
> When I call "msgctl08 100000 16" it completes fast.
> 
> Doing the follwing on the ref kernel:
> echo 1746 > /proc/sys/kernel/msgmni
> msgctl08 100000 1746
> 
> makes th test block too :-(
> 
> Will check to see where the problem comes from.
> 

Well, actually, the test does not block, it only takes much much more 
time to be executed:

doing this:
date; ./msgctl08 100000 XXX; date


gives us the following results:
XXX           16   32   64   128   256   512   1024   1746
time(secs)     2    4    8    16    32    64    132    241

XXX is the # of msg queues to be created = # of processes to be forked 
as readers = # of processes to be created as writers
time is approximative since it is obtained by a "date" before and after.

XXX used to be 16 before the patchset  ---> 1st column
     --> 16 processes forked as reader
     --> + 16 processes forked as writers
     --> + 16 msg queues
XXX = 1746 (on my victim) after the patchset ---> last column
     --> 1746 reader processes forked
     --> + 1746 writers forked
     --> + 1746 msg queues created

The same tests on the ref kernel give approximatly the same results.

So if we don't want this longer time to appear as a regression, the LTP 
should be changed:
1) either by setting the result of get_max_msgqueues() as the MSGMNI 
constant (16) (that would be the best solution in my mind)
2) or by warning the tester that it may take a long time to finish.

There would be 3 tests impacted:

kernel/syscalls/ipc/msgctl/msgctl08.c
kernel/syscalls/ipc/msgctl/msgctl09.c
kernel/syscalls/ipc/msgget/msgget03.c

Cc-ing ltp mailing list ...

Regards,
Nadia


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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Tony Luck]

On Mon, Feb 11, 2008 at 7:16 AM,  <Nadia.Derbey@bull.net> wrote:
>  Index: linux-2.6.24-mm1/ipc/msg.c
>  ===================================================================
>  --- linux-2.6.24-mm1.orig/ipc/msg.c     2008-02-07 15:02:29.000000000 +0100
>  +++ linux-2.6.24-mm1/ipc/msg.c  2008-02-07 15:24:19.000000000 +0100
...
>  +out_callback:
>  +
>  +       printk(KERN_INFO "msgmni has been set to %d for ipc namespace %p\n",
>  +               ns->msg_ctlmni, ns);
>  +}

This patch has now made its way to mainline.  I can see how this printk
was really useful to you while developing this patch. But does it add
much value in a production system? It just looks like another piece of
clutter on the console to my uncontainerized eyes.

-Tony

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Nadia Derbey]

Tony Luck wrote:
> On Mon, Feb 11, 2008 at 7:16 AM,  <Nadia.Derbey@bull.net> wrote:
> 
>> Index: linux-2.6.24-mm1/ipc/msg.c
>> ===================================================================
>> --- linux-2.6.24-mm1.orig/ipc/msg.c     2008-02-07 15:02:29.000000000 +0100
>> +++ linux-2.6.24-mm1/ipc/msg.c  2008-02-07 15:24:19.000000000 +0100
> 
> ...
> 
>> +out_callback:
>> +
>> +       printk(KERN_INFO "msgmni has been set to %d for ipc namespace %p\n",
>> +               ns->msg_ctlmni, ns);
>> +}
> 
> 
> This patch has now made its way to mainline.  I can see how this printk
> was really useful to you while developing this patch. But does it add
> much value in a production system? It just looks like another piece of
> clutter on the console to my uncontainerized eyes.
> 
> -Tony
> 
> 


Well, this printk had been suggested by somebody (sorry I don't remember 
who) when I first submitted the patch. Actually I think it might be 
useful for a sysadmin to be aware of a change in the msgmni value: we 
have the message not only at boot time, but also each time msgmni is 
recomputed because of a change in the amount of memory.
Also, at boot time, I think it's interesting to have the actual msgmni 
value: it used to unconditionally be set to 16. Some applications that 
used to need an initialization script setting msgmni to a higher value 
might not need that script anymore, since the new value might fit their 
needs.

Regards,
Nadia

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RE: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Luck, Tony]

> Well, this printk had been suggested by somebody (sorry I don't remember 
> who) when I first submitted the patch. Actually I think it might be 
> useful for a sysadmin to be aware of a change in the msgmni value: we 
> have the message not only at boot time, but also each time msgmni is 
> recomputed because of a change in the amount of memory.

If the message is directed at the system administrator, then it would
be nice if there were some more meaningful way to show the namespace
that is affected than just printing the hex address of the kernel structure.

As the sysadmin for my test systems, printing the hex address is mildly
annoying ... I now have to add a new case to my scripts that look at
dmesg output for unusual activity.

Is there some better "name for a namespace" than the address? Perhaps
the process id of the process that instantiated the namespace???

-Tony

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Serge E. Hallyn]

Quoting Luck, Tony (tony.luck@intel.com):
> > Well, this printk had been suggested by somebody (sorry I don't remember 
> > who) when I first submitted the patch. Actually I think it might be 
> > useful for a sysadmin to be aware of a change in the msgmni value: we 
> > have the message not only at boot time, but also each time msgmni is 
> > recomputed because of a change in the amount of memory.
> 
> If the message is directed at the system administrator, then it would
> be nice if there were some more meaningful way to show the namespace
> that is affected than just printing the hex address of the kernel structure.
> 
> As the sysadmin for my test systems, printing the hex address is mildly
> annoying ... I now have to add a new case to my scripts that look at
> dmesg output for unusual activity.
> 
> Is there some better "name for a namespace" than the address? Perhaps
> the process id of the process that instantiated the namespace???

I agree with Tony here.  Aside from the nuisance it is to see that
message on console every time I unshare a namespace, a printk doesn't
seem like the right way to output the info.  At most I'd say an audit
message.

-serge

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Nadia Derbey]

Serge E. Hallyn wrote:
> Quoting Luck, Tony (tony.luck@intel.com):
> 
>>>Well, this printk had been suggested by somebody (sorry I don't remember 
>>>who) when I first submitted the patch. Actually I think it might be 
>>>useful for a sysadmin to be aware of a change in the msgmni value: we 
>>>have the message not only at boot time, but also each time msgmni is 
>>>recomputed because of a change in the amount of memory.
>>
>>If the message is directed at the system administrator, then it would
>>be nice if there were some more meaningful way to show the namespace
>>that is affected than just printing the hex address of the kernel structure.
>>
>>As the sysadmin for my test systems, printing the hex address is mildly
>>annoying ... I now have to add a new case to my scripts that look at
>>dmesg output for unusual activity.
>>
>>Is there some better "name for a namespace" than the address? Perhaps
>>the process id of the process that instantiated the namespace???
> 
> 
> I agree with Tony here.  Aside from the nuisance it is to see that
> message on console every time I unshare a namespace, a printk doesn't
> seem like the right way to output the info.

But you agree that this is happening only because you're doing tests 
related to namespaces, right?
I don't think that in a "standard" configuration this will happen very 
frequently, but may be I'm wrong.

>  At most I'd say an audit
> message.
> 

That's a good idea. Thanks, Serge. I'll do that.

Regards,
Nadia

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Serge E. Hallyn]

Quoting Nadia Derbey (Nadia.Derbey@bull.net):
> Serge E. Hallyn wrote:
>> Quoting Luck, Tony (tony.luck@intel.com):
>>>> Well, this printk had been suggested by somebody (sorry I don't remember 
>>>> who) when I first submitted the patch. Actually I think it might be 
>>>> useful for a sysadmin to be aware of a change in the msgmni value: we 
>>>> have the message not only at boot time, but also each time msgmni is 
>>>> recomputed because of a change in the amount of memory.
>>>
>>> If the message is directed at the system administrator, then it would
>>> be nice if there were some more meaningful way to show the namespace
>>> that is affected than just printing the hex address of the kernel 
>>> structure.
>>>
>>> As the sysadmin for my test systems, printing the hex address is mildly
>>> annoying ... I now have to add a new case to my scripts that look at
>>> dmesg output for unusual activity.
>>>
>>> Is there some better "name for a namespace" than the address? Perhaps
>>> the process id of the process that instantiated the namespace???
>> I agree with Tony here.  Aside from the nuisance it is to see that
>> message on console every time I unshare a namespace, a printk doesn't
>> seem like the right way to output the info.
>
> But you agree that this is happening only because you're doing tests 
> related to namespaces, right?

Yup :)

> I don't think that in a "standard" configuration this will happen very 
> frequently, but may be I'm wrong.
>
>>  At most I'd say an audit
>> message.
>
> That's a good idea. Thanks, Serge. I'll do that.

It'll probably still end up a printk for me, but it'll be my own fault
for not setting up audit.

> Regards,
> Nadia

thanks,
-serge

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Matt Helsley]

On Wed, 2008-05-07 at 08:17 -0500, Serge E. Hallyn wrote:
> Quoting Nadia Derbey (Nadia.Derbey@bull.net):
> > Serge E. Hallyn wrote:
> >> Quoting Luck, Tony (tony.luck@intel.com):
> >>>> Well, this printk had been suggested by somebody (sorry I don't remember 
> >>>> who) when I first submitted the patch. Actually I think it might be 
> >>>> useful for a sysadmin to be aware of a change in the msgmni value: we 
> >>>> have the message not only at boot time, but also each time msgmni is 
> >>>> recomputed because of a change in the amount of memory.
> >>>
> >>> If the message is directed at the system administrator, then it would
> >>> be nice if there were some more meaningful way to show the namespace
> >>> that is affected than just printing the hex address of the kernel 
> >>> structure.
> >>>
> >>> As the sysadmin for my test systems, printing the hex address is mildly
> >>> annoying ... I now have to add a new case to my scripts that look at
> >>> dmesg output for unusual activity.
> >>>
> >>> Is there some better "name for a namespace" than the address? Perhaps
> >>> the process id of the process that instantiated the namespace???
> >> I agree with Tony here.  Aside from the nuisance it is to see that
> >> message on console every time I unshare a namespace, a printk doesn't
> >> seem like the right way to output the info.
> >
> > But you agree that this is happening only because you're doing tests 
> > related to namespaces, right?
> 
> Yup :)
> 
> > I don't think that in a "standard" configuration this will happen very 
> > frequently, but may be I'm wrong.
> >
> >>  At most I'd say an audit
> >> message.
>
> > That's a good idea. Thanks, Serge. I'll do that.

	I'm not familiar with kernel policies regarding audit messages. Are
audit messages treated anything like kernel interfaces when it comes to
removing/changing them?

Cheers,
	-Matt Helsley

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Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem

[Nadia Derbey]

Luck, Tony wrote:
>>Well, this printk had been suggested by somebody (sorry I don't remember 
>>who) when I first submitted the patch. Actually I think it might be 
>>useful for a sysadmin to be aware of a change in the msgmni value: we 
>>have the message not only at boot time, but also each time msgmni is 
>>recomputed because of a change in the amount of memory.
> 
> 
> If the message is directed at the system administrator, then it would
> be nice if there were some more meaningful way to show the namespace
> that is affected than just printing the hex address of the kernel structure.
> 
> As the sysadmin for my test systems, printing the hex address is mildly
> annoying ... I now have to add a new case to my scripts that look at
> dmesg output for unusual activity.
> 
> Is there some better "name for a namespace" than the address? Perhaps
> the process id of the process that instantiated the namespace???
> 

Unfortunately no when we are inside an ipc namespace, we don't have such 
interesting informations. But I agree with you, an address is not 
readable enough. I'll try to find a solution.

Regards,
Nadia

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