Date: Fri, 17 Aug 2012 10:55:21 +0400 From: Andrey Zonov <andrey@zonov.org> To: Marie Bacuno II <gezeala@gmail.com> Cc: Garrett Cooper <yanegomi@gmail.com>, "freebsd-performance@freebsd.org" <freebsd-performance@freebsd.org> Subject: Re: vm.kmem_size_max and vm.kmem_size capped at 329853485875 (~307GB) Message-ID: <502DEAD9.6050304@zonov.org> In-Reply-To: <B74BE4AB-AB67-45BD-BFC3-9AE33A85751C@gmail.com> References: <CAJKO3mU8bfn=jmWNSpvAXOR1AWyAAM0Sio1D1PnOYg8P59V9cg@mail.gmail.com> <CAGH67wS=jue7%2B92jSCyaydOLHC=hPwtndV64FVtC7nhDsPvFng@mail.gmail.com> <CAGH67wTNfW45pgJ_%2BVn_sX%2BP9M5B5wzPT9270dRmWjYF6KerrA@mail.gmail.com> <B74BE4AB-AB67-45BD-BFC3-9AE33A85751C@gmail.com>
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On 8/17/12 7:15 AM, Marie Bacuno II wrote: > > On Aug 16, 2012, at 18:47, Garrett Cooper <yanegomi@gmail.com> wrote: > >> On Thu, Aug 16, 2012 at 6:44 PM, Garrett Cooper <yanegomi@gmail.com> wrote: >>> On Thu, Aug 16, 2012 at 5:46 PM, Gezeala M. Bacuño II <gezeala@gmail.com> wrote: >>>> Hello fellow listers, >>>> >>>> On a server with 512GB RAM it appears that vm.kmem_size_max is not >>>> being auto-tuned to use >329853485875 (~307GB). >>>> >>>> On this machine vm.kmem_size is equal to vm.kmem_size_max >>>> >>>> # from sysctl >>>> vm.kmem_size_max: 329853485875 >>>> vm.kmem_size: 329853485875 >>>> >>>> On a machine with 1GB of RAM, I have successfully set vm.kmem_size_max >>>> to 330GB and vm.kmem_size automatically adjusts to 1GB even if I >>>> manually set it in /boot/loader.conf. >>>> >>>> But on the machine with 512GB of RAM it just resets. For the machine >>>> to boot, we need to go to the loader prompt and issue: >>>> >>>> OK set vm.kmem_size_max="300G" >>>> OK boot >>>> >>>> On all PCBSD (8,9) or FreeBSD (8.1,8.2,9) machines we have, >>>> vm.kmem_size_max is always set to 329853485875. >>>> >>>> How can I increase vm.kmem_size_max to use at least 500GB? And how is >>>> 329853485875 determined (formula)? I need to increase vm.kmem_size_max >>>> and vm.kmem_size so I can set vfs.zfs.arc_max (ZFS ARC) to use say >>>> 490GB. >>>> >>>> I'm browsing thru the source code at >>>> http://fxr.watson.org/fxr/search?v=FREEBSD9&string=vm.kmem_size_max >>>> and I'm still trying to make sense of how vm.kmem_size_max is >>>> computed. >>>> >>>> I have posted the same topic on forums.freebsd.org but I'm not getting >>>> any recommendations. >>>> >>>> Please see the link for additional details: >>>> http://forums.freebsd.org/showthread.php?t=33977 >>> >>> Have you tried defining VM_KMEM_SIZE_MAX to your target value? >>> >>> Its architecture specific BTW... see >>> sys/<architecture>/include/vmparam.h -- look for `VM_KMEM_SIZE_MAX`. >> >> Also, it's a tunable, not a sysctl... so you need to set the value in >> /boot/loader.conf . >> -Garrett > > Thanks for the quick reply. > > Yes, had it set on /boot/loader.conf and by trial and error on the loader prompt. > > We were able to bump it to 400G successfully. Tried 500G and 450G and the machine just spews out garbage in the screen. > > The latest output from "zfs-stats -a" with vm.kmem_size_max="400G" is in the forum: http://forums.freebsd.org/showthread.php?t=33977 > > About the code, I am looking into amd64 arch. Still checking the values of the variables.. Can't just retrieve them using getconf. If you can point me to a doxygen like documentation appreciate it a lot. > > Where does the constant value 329853485875 came from? > It comes from this macro: #define VM_KMEM_SIZE_MAX ((VM_MAX_KERNEL_ADDRESS - \ VM_MIN_KERNEL_ADDRESS + 1) * 3 / 5) ((1<<39) * 3 / 5) = 329853488332 AFAIK, VM_MAX_KERNEL_ADDRESS is limited to 512Gb. May be it's time to increase it again. I would asked kib@ or alc@ about that. -- Andrey Zonov
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