Re: Problem with lots of (perhaps too much?) memory

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

> On 16. May 2017, at 23:25, Paul Goyette <paul%whooppee.com@localhost> wrote:
> 
> On Tue, 16 May 2017, Joerg Sonnenberger wrote:
> 
>> On Tue, May 16, 2017 at 08:12:20AM +0800, Paul Goyette wrote:
>>> * xosview frequently reports that the system is running at near-100%
>>>  in SYS time.
>> 
>> Chances are very high that you are hitting the free page lock contention
>> bug.
> 
> Further observation:
> 
> 1. A run of lockstat shows that there's lots of activity on
>   mntvnode_lock from vfs_insmntque
> 
> 2. The problem can be triggered simply by running 'du -s' on a
>   file system with lots of files (for example, after having run
>   'build.sh release' for ~40 different architectures, and having
>   kept ALL of the obj/*, dest/*, and release/* output files).
> 
> 3. The ioflush thread _never_ finishes.  Even 12 hours after the
>   trigger, and after an 8-hour sleep window doing nothing (other
>   than receiving a couple dozen Emails), the ioflush thread is
>   still using 5-10% of one CPU core/thread.
> 
> 4. If I umount the trigger file system, ioflush time goes to near-
>   zero.  I can remount without problem, however shortly after
>   re-running the 'du -s' command the problem returns.
> 
> There was a comment on IRC that yamt@ had been working on a problem where "ioflush wastes a lot of CPU time when there are lots of vnodes" seems to describe this situation.  Unfortunately, it seems that yamt never finished working on the problem.  :(

Two questions:

- What is the size of your vnode cache (sysctl kern.maxvnodes)?

- Is the vdrain thread using CPU too?

--
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig (Germany)