Date: Fri, 21 Jan 2011 12:44:13 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Sergey Kandaurov <pluknet@gmail.com> Subject: Re: [rfc] allow to boot with >= 256GB physmem Message-ID: <201101211244.13830.jhb@freebsd.org> In-Reply-To: <AANLkTikt5=2L0rHyGbsjvG8eV6Ve4JkRM_pcyNiAsPu8@mail.gmail.com> References: <AANLkTikt5=2L0rHyGbsjvG8eV6Ve4JkRM_pcyNiAsPu8@mail.gmail.com>
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On Friday, January 21, 2011 11:09:10 am Sergey Kandaurov wrote: > Hello. > > Some time ago I faced with a problem booting with 400GB physmem. > The problem is that vm.max_proc_mmap type overflows with > such high value, and that results in a broken mmap() syscall. > The max_proc_mmap value is a signed int and roughly calculated > at vmmapentry_rsrc_init() as u_long vm_kmem_size quotient: > vm_kmem_size / sizeof(struct vm_map_entry) / 100. > > Although at the time it was introduced at svn r57263 the value > was quite low (f.e. the related commit log stands: > "The value defaults to around 9000 for a 128MB machine."), > the problem is observed on amd64 where KVA space after > r212784 is factually bound to the only physical memory size. > > With INT_MAX here is 0x7fffffff, and sizeof(struct vm_map_entry) > is 120, it's enough to have sligthly less than 256GB to be able > to reproduce the problem. > > I rewrote vmmapentry_rsrc_init() to set large enough limit for > max_proc_mmap just to protect from integer type overflow. > As it's also possible to live tune this value, I also added a > simple anti-shoot constraint to its sysctl handler. > I'm not sure though if it's worth to commit the second part. > > As this patch may cause some bikeshedding, > I'd like to hear your comments before I will commit it. > > http://plukky.net/~pluknet/patches/max_proc_mmap.diff Is there any reason we can't just make this variable and sysctl a long? -- John Baldwin
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