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From: "Michael Kerrisk" <>
Cc: "Linux Kernel Mailing List" <>,
Subject: Re: [PATCH 1/8] Scaling msgmni to the amount of lowmem
Date: Tue, 20 May 2008 16:28:27 +0200	[thread overview]
Message-ID: <> (raw)

Hello Nadia,

Regarding your:

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

The man page (
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

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?



Michael Kerrisk
Linux man-pages maintainer;
Found a bug?

             reply	other threads:[~2008-05-20 14:28 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-05-20 14:28 Michael Kerrisk [this message]
2008-05-20 14:45 ` Nadia Derbey
2008-05-20 14:56   ` Michael Kerrisk
2008-05-21 10:47   ` Michael Kerrisk
  -- strict thread matches above, loose matches on Subject: below --
2008-02-11 14:16 [PATCH 0/8] Change default MSGMNI tunable to scale with lowmem (v3) Nadia.Derbey
2008-02-11 14:16 ` [PATCH 1/8] Scaling msgmni to the amount of lowmem Nadia.Derbey
2008-02-16  5:59   ` Andrew Morton
2008-02-18  9:19     ` Nadia Derbey
2008-02-18 13:08       ` Nadia Derbey
2008-04-29 20:28   ` Tony Luck
2008-05-05  8:45     ` Nadia Derbey
2008-05-06 16:42       ` Luck, Tony
2008-05-06 18:05         ` Serge E. Hallyn
2008-05-07  5:37           ` Nadia Derbey
2008-05-07 13:17             ` Serge E. Hallyn
2008-05-07 18:12               ` Matt Helsley
2008-05-07  5:13         ` Nadia Derbey

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