Date: Tue, 05 Apr 2005 05:26:01 -0700 From: ray@redshift.com To: freebsd-hackers@FreeBSD.ORG Subject: Kernel [memory] tweaking question Message-ID: <3.0.1.32.20050405052601.00ab4388@pop.redshift.com> In-Reply-To: <42518AC9.5070208@comcast.net>
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I'm doing some tweaking on my kernel tonight (FreeBSD 5.3) and I'm trying to get a better grip on what the following lines do and what impact they could have to the overall performance of a server: options SHMALL= options SHMMAX= options SHMMAXPGS= options SHMMIN= options SHMMNI= options SHMSEG= I understand these control shared memory and how many semaphores the kernel can allocate, 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. In other words, for something like Apache, how much shared memory is required? Or what would adding additional shared memory and/or semaphores provide. Does the default # provided for by FreeBSD create a problem and/or would it use additional ram if allocated? 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? Just hearing "you get more memory" doesn't really explain what the OS can do with it, or what not having enough could limit, etc. Thanks! Ray
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