From mboxrd@z Thu Jan 1 00:00:00 1970 From: Manfred Spraul Subject: MSGMNB and MSGMAX: good default values? Date: Sat, 31 May 2014 19:54:36 +0200 Message-ID: <538A175C.80705@colorfullife.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-kernel-owner@vger.kernel.org To: Linux API , Linux Kernel Mailing List , Michael Kerrisk , Davidlohr Bueso List-Id: linux-api@vger.kernel.org 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