Date: Mon, 22 Apr 2002 23:17:07 -0700 From: David Schultz <dschultz@uclink.berkeley.edu> To: Terry Lambert <tlambert2@mindspring.com> Cc: freebsd-current@FreeBSD.ORG, freebsd-stable@FreeBSD.ORG Subject: Re: FreeBSD 4.5-STABLE not easily scalable to large servers ... ? Message-ID: <20020422231707.A53736@HAL9000.wox.org> In-Reply-To: <3CC4C3A0.B1279BFC@mindspring.com>; from tlambert2@mindspring.com on Mon, Apr 22, 2002 at 07:14:56PM -0700 References: <20020421191440.J1721-100000@mail1.hub.org> <3CC3D494.649C2A8E@mindspring.com> <20020422060952.B31888@HAL9000.wox.org> <3CC4C3A0.B1279BFC@mindspring.com>
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Thus spake Terry Lambert <tlambert2@mindspring.com>: > I'm pretty sure Solaris also used 4K pages for swappable memory > in the kernel, as well: 4M pages don't make much sense, since > you could, for example, exhaust KVA space with 250 kernel modules > (250 X (1 data + 1 code) * 4M = 2G). It doesn't use 4M pages for all kernel memory---just the first 4M of code and the first 4M of data. Supposedly it also allows applications to take advantage of 4M pages, though I'm not sure how that works. At the very least I'd suppose that those pages are locked into memory. > I don't know where the Linux limitation comes from; it's really > hard for me to believe "~3G", since it's not an even power of 2, > so I don't really credit this limitation. I don't really understand it either. I could try to find the link to where I found this information if you're interested, but I wouldn't be surprised if it is simply wrong. The 2.4 kernel docs seem to imply that 2.4 can use 4 GB of RAM without PAE. > No problem; I think you will have to, if you are planning on > mucking about with more than 4G of physical memory. I have no such plans in the immediate future; at this point the discussion is a curiosity. But with any luck I will already know what's going on by the time I need to worry about tweaking the kernel in bizarre ways. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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