Suddenly slow lstat syscalls on CURRENT from Juli

Beat Gätzi beat at
Sun Jan 2 14:51:09 UTC 2011

On 02.01.2011 01:36, Julian Elischer wrote:
> On 1/1/11 9:26 AM, Kostik Belousov wrote:
>> On Sat, Jan 01, 2011 at 05:59:10PM +0100, Beat G?tzi wrote:
>>> On 01.01.2011 17:46, Kostik Belousov wrote:
>>>> On Sat, Jan 01, 2011 at 05:42:58PM +0100, Beat G?tzi wrote:
>>>>> On 01.01.2011 17:12, Kostik Belousov wrote:
>>>>>> On Sat, Jan 01, 2011 at 05:00:56PM +0100, Beat G?tzi wrote:
>>>>>>> On 01.01.2011 16:45, Kostik Belousov wrote:
>>>>>>>> Check the output of sysctl kern.maxvnodes and vfs.numvnodes. I
>>>>>>>> suspect
>>>>>>>> they are quite close or equial. If yes, consider increasing
>>>>>>>> maxvnodes.
>>>>>>>> Another workaround, if you have huge nested directories
>>>>>>>> hierarhy, is
>>>>>>>> to set vfs.vlru_allow_cache_src to 1.
>>>>>>> Thanks for the hint. kern.maxvnodes and vfs.numvnodes were equal:
>>>>>>> # sysctl kern.maxvnodes vfs.numvnodes
>>>>>>> kern.maxvnodes: 100000
>>>>>>> vfs.numvnodes: 100765
>>>>>>> I've increased kern.maxvnodes and the problem was gone until
>>>>>>> vfs.numvnodes reached the value of kern.maxvnodes again:
>>>>>>> # sysctl kern.maxvnodes vfs.numvnodes
>>>>>>> kern.maxvnodes: 150000
>>>>>>> vfs.numvnodes: 150109
>>>>>> The processes should be stuck in "vlruwk" state, that can be
>>>>>> checked with ps or '^T' on the terminal.
>>>>> Yes, there are various processes in "vlruwk" state,
>>>>>>> As the directory structure is quite huge on this server I've set
>>>>>>> vfs.vlru_allow_cache_src to one now.
>>>>>> Did it helped ?
>>>>> No, it doesn't looks like setting vfs.vlru_allow_cache_src helped. The
>>>>> problem was gone when I increased kern.maxvnodes until vfs.numvnodes
>>>>> reached that level. I've stopped all running deamons but numvnodes
>>>>> doesn't decrease.
>>>> Stopping the daemons would not decrease the count of cached vnodes.
>>>> What you can do is to call unmount on the filesystems. Supposedly, the
>>>> filesystems are busy and unmount shall fail, but it will force freed
>>>> the vnodes that are unused by any process.
>>> That freed around 1500 vnodes. At the moment the vfs.numvnodes doesn't
>>> increase rapidly and the server is usable. I will keep an eye it to see
>>> if I run into the same problem again.
>> This is too small amount of vnodes to be freed for the typical system,
>> and it feels like a real vnode leak. It would be helpful if you tried
>> to identify the load that causes the situation to occur.
>> You are on the UFS, right ?
> try running sockstat to a file and looking to see what is open..
> it could just be a normal leak.

The sockstat output looks normal at least to me:


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