Date: Mon, 27 Aug 2012 15:23:05 -0700 From: =?ISO-8859-1?Q?Gezeala_M=2E_Bacu=F1o_II?= <gezeala@gmail.com> To: Alan Cox <alc@rice.edu> Cc: alc@freebsd.org, freebsd-performance@freebsd.org, Andrey Zonov <andrey@zonov.org>, kib@freebsd.org Subject: Re: vm.kmem_size_max and vm.kmem_size capped at 329853485875 (~307GB) Message-ID: <CAJKO3mW%2BJ55NFJiJS4sULi9Bq23ZCSj_oBxGN407YhJL=EqvWg@mail.gmail.com> In-Reply-To: <50367E5D.1020702@rice.edu> 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> <502DEAD9.6050304@zonov.org> <CAJKO3mVWOFa9Cby_EWsf_OFHux7YBGSV7aGYSP2YANeJkqZtoQ@mail.gmail.com> <CAJKO3mU1NdkQwNSEDk3wWyLN700=dQ0_jSXt_sx-ABpywNjfsg@mail.gmail.com> <502EB081.3030801@rice.edu> <CAJKO3mWEXUvLtdSvmjgNhhyVqw4j0DuTYm9MqLd9=i9==WLAaA@mail.gmail.com> <502FE98E.40807@rice.edu> <CAJKO3mVUMRfkUpSuk0fDdnEMc3hr087iH5u8b5N60CnPs-gP1g@mail.gmail.com> <50325634.7090904@rice.edu> <CAJKO3mXPZVhLo=si%2BEoFPGD5R_m297xedRFY-0N__WOsZBaiCA@mail.gmail.com> <CAJKO3mXQ2_XrdxWgE6JRVOpMu_cEBa_=nJCxFDJ%2BJ=f5_OUsPQ@mail.gmail.com> <503418C0.5000901@rice.edu> <CAJKO3mUkjEbY=t6K5MGphMQ_myxUHnScP8gy8v3J%2BARFMf15=g@mail.gmail.com> <50367E5D.1020702@rice.edu>
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On Thu, Aug 23, 2012 at 12:02 PM, Alan Cox <alc@rice.edu> wrote:
> On 08/22/2012 12:09, Gezeala M. Bacu=F1o II wrote:
>>
>> On Tue, Aug 21, 2012 at 4:24 PM, Alan Cox<alc@rice.edu> wrote:
>>>
>>> On 8/20/2012 8:26 PM, Gezeala M. Bacu=F1o II wrote:
>>>>
>>>> On Mon, Aug 20, 2012 at 9:07 AM, Gezeala M. Bacu=F1o II<gezeala@gmail.=
com>
>>>> wrote:
>>>>>
>>>>> On Mon, Aug 20, 2012 at 8:22 AM, Alan Cox<alc@rice.edu> wrote:
>>>>>>
>>>>>> On 08/18/2012 19:57, Gezeala M. Bacu=F1o II wrote:
>>>>>>>
>>>>>>> On Sat, Aug 18, 2012 at 12:14 PM, Alan Cox<alc@rice.edu> wrote:
>>>>>>>>
>>>>>>>> On 08/17/2012 17:08, Gezeala M. Bacu=F1o II wrote:
>>>>>>>>>
>>>>>>>>> On Fri, Aug 17, 2012 at 1:58 PM, Alan Cox<alc@rice.edu> wrote:
>>>>>>>>>>
>>>>>>>>>> vm.kmem_size controls the maximum size of the kernel's heap, i.e=
.,
>>>>>>>>>> the
>>>>>>>>>> region where the kernel's slab and malloc()-like memory allocato=
rs
>>>>>>>>>> obtain
>>>>>>>>>> their memory. While this heap may occupy the largest portion of
>>>>>>>>>> the
>>>>>>>>>> kernel's virtual address space, it cannot occupy the entirety of
>>>>>>>>>> the
>>>>>>>>>> address
>>>>>>>>>> space. There are other things that must be given space within t=
he
>>>>>>>>>> kernel's
>>>>>>>>>> address space, for example, the file system buffer map.
>>>>>>>>>>
>>>>>>>>>> ZFS does not, however, use the regular file system buffer cache.
>>>>>>>>>> The
>>>>>>>>>> ARC
>>>>>>>>>> takes its place, and the ARC abuses the kernel's heap like nothi=
ng
>>>>>>>>>> else.
>>>>>>>>>> So, if you are running a machine that only makes trivial use of =
a
>>>>>>>>>> non-ZFS
>>>>>>>>>> file system, like you boot from UFS, but store all of your data =
in
>>>>>>>>>> ZFS,
>>>>>>>>>> then
>>>>>>>>>> you can dramatically reduce the size of the buffer map via boot
>>>>>>>>>> loader
>>>>>>>>>> tuneables and proportionately increase vm.kmem_size.
>>>>>>>>>>
>>>>>>>>>> Any further increases in the kernel virtual address space size
>>>>>>>>>> will,
>>>>>>>>>> however, require code changes. Small changes, but changes
>>>>>>>>>> nonetheless.
>>>>>>>>>>
>>>>>>>>>> Alan
>>>>>>>>>>
>>>>> <<snip>>
>>>>>>>>
>>>>>>>> Your objective should be to reduce the value of "sysctl
>>>>>>>> vfs.maxbufspace".
>>>>>>>> You can do this by setting the loader.conf tuneable "kern.maxbcach=
e"
>>>>>>>> to
>>>>>>>> the
>>>>>>>> desired value.
>>>>>>>>
>>>>>>>> What does your machine currently report for "sysctl
>>>>>>>> vfs.maxbufspace"?
>>>>>>>>
>>>>>>> Here you go:
>>>>>>> vfs.maxbufspace: 54967025664
>>>>>>> kern.maxbcache: 0
>>>>>>
>>>>>>
>>>>>> Try setting kern.maxbcache to two billion and adding 50 billion to t=
he
>>>>>> setting of vm.kmem_size{,_max}.
>>>>>>
>>>> 2 : 50 =3D=3D>> is this the ratio for further tuning
>>>> kern.maxbcache:vm.kmem_size? Is kern.maxbcache also in bytes?
>>>>
>>> No, this is not a ratio. Yes, kern.maxbcache is in bytes. Basically, f=
or
>>> every byte that you subtract from vfs.maxbufspace, through setting
>>> kern.maxbcache, you can add a byte to vm.kmem_size{,_max}.
>>>
>>> Alan
>>>
>> Great! Thanks. Are there other sysctls aside from vfs.bufspace that I
>> should monitor for vfs.maxbufspace usage? I just want to make sure
>> that vfs.maxbufspace is sufficient for our needs.
>
>
> You might keep an eye on "sysctl vfs.bufdefragcnt". If it starts rapidly
> increasing, you may want to increase vfs.maxbufspace.
>
> Alan
>
We seem to max out vfs.bufspace in <24hrs uptime. It has been steady
at 1999273984 while vfs.bufdefragcnt stays at 0 - which I presume is
good. Nevertheless, I will increase kern.maxbcache to 6GB and adjust
vm.kmem_size{,_max}, vfs.zfs.arc_max accordingly. On another machine
with vfs.maxbufspace auto-tuned to 7738671104 (~7.2GB), vfs.bufspace
is now at 5278597120 (uptime 129 days).
vfs.maxbufspace: 1999994880
kern.maxbcache: 2000000000
vfs.hirunningspace: 16777216
vfs.lorunningspace: 11206656
vfs.bufdefragcnt: 0
vfs.buffreekvacnt: 59
vfs.bufreusecnt: 61075
vfs.hibufspace: 1999339520
vfs.lobufspace: 1999273984
vfs.maxmallocbufspace: 99966976
vfs.bufmallocspace: 0
vfs.bufspace: 1999273984
vfs.runningbufspace: 0
vfs.numdirtybuffers: 2
vfs.lodirtybuffers: 15268
vfs.hidirtybuffers: 30537
vfs.dirtybufthresh: 27483
vfs.numfreebuffers: 122068
vfs.getnewbufcalls: 1159148
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