From owner-freebsd-hackers@FreeBSD.ORG Thu Apr 7 08:51:06 2005 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 31CD616A4CE for ; Thu, 7 Apr 2005 08:51:06 +0000 (GMT) Received: from outgoing.redshift.com (outgoing.redshift.com [207.177.231.8]) by mx1.FreeBSD.org (Postfix) with ESMTP id D1FE043D39 for ; Thu, 7 Apr 2005 08:51:05 +0000 (GMT) (envelope-from ray@redshift.com) Received: from workstation (216-228-19-21.dsl.redshift.com [216.228.19.21]) by outgoing.redshift.com (Postfix) with SMTP id E8E6E97047; Thu, 7 Apr 2005 01:51:04 -0700 (PDT) Message-Id: <3.0.1.32.20050407015121.00aaeee8@pop.redshift.com> X-Mailer: na X-Sender: redshift.com Date: Thu, 07 Apr 2005 01:51:21 -0700 To: Peter Jeremy From: ray@redshift.com In-Reply-To: <20050407083639.GD57256@cirb503493.alcatel.com.au> References: <3.0.1.32.20050405052601.00ab4388@pop.redshift.com> <42518AC9.5070208@comcast.net> <3.0.1.32.20050405052601.00ab4388@pop.redshift.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" cc: freebsd-hackers@freebsd.org Subject: Re: Kernel [memory] tweaking question X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Apr 2005 08:51:06 -0000 Great run down, thanks Peter - I will do more checking in those areas. Ray At 06:36 PM 4/7/2005 +1000, Peter Jeremy wrote: | On Tue, 2005-Apr-05 05:26:01 -0700, ray@redshift.com wrote: | >options SHMALL= | >options SHMMAX= | >options SHMMAXPGS= | >options SHMMIN= | >options SHMMNI= | >options SHMSEG= | | These are all reasonably well documented in sys/conf/NOTES. If you | want more detail, try a SystemV-oriented Unix book | | >I understand these control shared memory and how many semaphores the | >kernel can allocate, | | Close - they only control SystemV shared memory. Sane shared memory | is available via mmap(2). SystemV semaphores are controlled via | SEMxxx options. Posix semaphores are listed as 'experimental'. | | > but I guess what I'm not 100% clear on is how | >the kernel uses these resources when it comes to running something | >like Apache or MySQL on a heavily loaded server. | | These values all define limits on the amount of shared memory | available system-wide (SHMALL and SHMMNI) and to a single process | (remaining options). As far as I can tell, neither Apache nor MySQL | use any SystemV IPC on FreeBSD. (The only thing that I've found that | does use SHM is X in some modes). | | > In other words, for | >something like Apache, how much shared memory is required? | | None. | | > Or what | >would adding additional shared memory and/or semaphores provide. | | Nothing. | | >Does the default # provided for by FreeBSD create a problem and/or | >would it use additional ram if allocated? | | Actually using SystemV IPC will use additional RAM. | | >Is there the anyone on the list that has experience with changing | >these that can provide a clear, down to earth explanation as to their | >impacts? | | I have used them on other Unices but never needed to tweak them on | FreeBSD. Before adjusting anything, use ipcs(1) to confirm that | they are being used. If you seem to be reaching limits (ipcs shows | that you are close to system limits or the applications are reporting | allocation errors), then just increase the parameter related to | whatever you are running out of. | | -- | Peter Jeremy | |