Date: Thu, 5 Dec 2002 14:53:46 +0300 (MSK) From: Varshavchick Alexander <alex@metrocom.ru> To: Terry Lambert <tlambert2@mindspring.com> Cc: <freebsd-questions@FreeBSD.ORG>, <freebsd-hackers@FreeBSD.ORG> Subject: Re: maxusers and random system freezes Message-ID: <Pine.GSO.4.33.0212051438100.7912-100000@apache.metrocom.ru> In-Reply-To: <3DEF37AF.182DD85@mindspring.com>
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On Thu, 5 Dec 2002, Terry Lambert wrote: ... > > Are you talking primarily about SHMMAXPGS=262144 option here? Then may be > > it'll be oevrall better to reduce it and make KVA space 2G, to leave more > > room for user address space? > > That's the one I was referring to, yes, but you didn't post your > whole config (please do *NOT* post it; I can't spend the time on > going over it line by line). > All other config options are pretty much like the default ones. > Tuning is a skill; it can be plotted out as a cookbook recipe, > but it takes a lot of work to do that, and no one has volunteered. > > Basically, to write out a cookbook, you have to know where every > byte of memory is going in the kernel, and what tunables impact > each other, and how they are related. > > Once you know that, you could easily write a program to kick out > a configuration file for various usages, or even modify the code > to auto-tune itself (everything by KVA space, which impacts the > base address that the kernel gets linked to... unless you compile > the entire kernel PIC, which I do not recommend). But knowing > the information is hard. I know it for 4.3 and 4.4. > You're right, expecially for getting an _ideally_ tuned kernel. However in a real life, a specialist cannot have an absolute knowledge about _all_ server and other issues, so practical solutions are being looked for in items which can arise. Of cause, no one is arguing that a basic knowledge is needed and required. ... > If you are having system freeses at random, and you want to fix > them instead of living with them, some experimentation is going > to be inevitable. I don't know enough about your installation > to be able to give you a kernel config file to use that will > magically fix all your current issues for you, and prevent future > issues from coming up. That's going to have to be up to you. > > Surely, I'm just trying to reduce the experimental attempts as much as possible and to rise the chances of success for each new configuration version. ... > > No, the swap is very slightly used on this server, and the total swap > > size is 2G. > > It doesn't matter. The amount of swap the kernel allocates page > tables for is based on the amount of physical RAM in the machine. > You pay for the page tables whether you use them or not, for swap, > for the kernel, and for any memory which you permit to be allocated > at interrupt time, plus any allocations that occur after you are up > and running, until you run out of physical RAM. > > This is "one of those things" you just have to know about how > the kernel uses virtual memory, if you are going to be a skilled > kernel tuner. > > > As a rule, swap should be at least physical memory size + 64K on > any system that you need to be able to get a system dump from, > since it needs to dump physical RAM. If you are not worried about > the machine falling over, then you can ignore that. > > Note that "man tuning" suggests 2* physical RAM for swap. > > PS: I am going to be out of touch (able to download, but not > send email) for the next couple of days... up to a week. If you > have more questions, and they can't wait, you will need to ask > someone else. > Thank you for all your advices, they've already helped a bit. Have luck in your trip or elsewhere. ----- Alex To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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