linux-kernel - MSGMNB and MSGMAX: good default values?

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Message-ID: <538A175C.80705@colorfullife.com>
Date:	Sat, 31 May 2014 19:54:36 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Linux API <linux-api@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Davidlohr Bueso <davidlohr@...com>
Subject: MSGMNB and MSGMAX: good default values?

Hi all,

until now, every sysadmin/distro had to update the sysv limits.
For shm, the new proposal is to increase the limits to (nearly) ULONG_MAX.

Right now, I try to create patches that also increase the limits for 
sysv msg, but I got stuck:

- MSGMNI is trivial, just increase it to nearly IPCMNI.

- MSGMNB is not an upper limit, it is actually the default amount of 
data that can be stored in a message queue before senders must sleep.
   Since Linux-0.99.10, it always was 16384.

   A websearch shows that for both db2 and oracle, the recommendation is 
65536.

   It seems that redhat has increased the value to 65536:
https://bugzilla.redhat.com/show_bug.cgi?id=862597

Tuxedo seems to use sysv messages and the documentation warns that too 
large values are harmfull:
http://read.pudn.com/downloads142/doc/618733/tux-a11-80/manual/13-ADM-PERF-Notes.pdf

- MSGMAX: Same issue as above: it was slightly below 4096 and since 2.6 
it is 8192.

Any proposals?
Right now, I would leave MSGMAX and MSGMNB as they are.

--
     Manfred
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